[0001] The present invention departs generally from the need of canceling wind disturbances
from desired acoustical source reception as of speech or music etc. Wind noise in
hearing devices is a severe problem. Wind noise may reach magnitudes of 100 dB SPL
(Sound Pressure Level) and even more. Users of hearing devices therefore often switch
their device off in windy conditions, because acoustical perception with the hearing
device in windy surrounding may become worse than without the hearing device.
[0002] Approaches are known to counteract wind noise by mechanical constructional measures,
but cannot eliminate wind noise completely, often even not to a completely satisfying
degree. It is well-known that wind noise is a low-frequency phenomenon. Depending
upon wind speed, direction of the wind with respect to the device, hair length of
the individual, mechanical obstructions like hats and other factors, magnitude and
spectral content of wind noise vary significantly. With respect to noise, effects
and causes we refer to
H. Dillon et al., "The sources of wind noise in hearing aids", IHCON 2000, as well as to I. Roe et al., "Wind noise in hearing aids: Causes and effects", submitted
to JASA.
[0003] Wind signals at sensing ports or acoustical/electrical input converters of hearing
devices mounted with a predetermined spacing are far less correlated than are normal
acoustical signals to be perceived, as especially speech, music etc.
[0004] One reason is that such normal acoustical signals arrive as more or less planar waves,
causing at distant acoustical to electrical input converters time delays which are
far predominantly caused by the direction of arrival with which such signals impinge
upon the converter. As known to the skilled artisan, this time delay is used in beamformer
art, whereby a delayed output signal from one converter is subtracted from the output
signal of the other converter. There results at the common output of subtraction a
signal which has an amplification characteristic with respect to impinging acoustical
signals which is dependent on the direction of arrival DOA of such signals with respect
to the converters and is commonly known as beamformer characteristics.
[0005] The subtraction of well correlated signals as generated by the above mentioned normal
signals to be perceived as of speech or music signals normally leads to the known
roll-off behavior of such beamformers. The roll-off behavior or characteristic establishes
a frequency dependent attenuation of the beam characteristics. It has a pronounced
high-pass character, which considerably attenuates low frequencies which are critical
especially for speech perception.
[0006] Wind noise signals are not subject to the the roll-off behavior of a beamformer because
of their lower correlation even at very low frequencies and considered at at least
two spaced apart input converters. Whereas normal signals as speech is attenuated
by the roll-off towards low frequencies, wind noise is not. Even worse, wind noise
has a further adverse effect on signal transfer of normal signals affecting speech
recognition. It masks speech-caused signals due to the "upwards-spread-off masking".
Upward-spread-off masking is a phenomenon according to which a signal at a predetermined
spectral frequency masks signals at higher frequency increasingly with increasing
amplitude.
[0007] From the
US 2002-0 037 088 A1 as well as from the
DE 10 045 197 it is known to tackle the problem of wind noise by detecting such noise at two spaced-apart
input converters and use in windy situations only the output signal of one of the
omnidirectional converters, thereby in fact switching beamforming off. Further, a
static high-pass filter is switched on to further attenuate wind noise.
[0008] Nevertheless, many hearing devices do not feature two or more acoustical input converters,
so that the detection and elimination of wind noise based on two or more converters
is not always possible. Further, as was mentioned above, the spectral shape of wind
noise varies significantly in time. Thereby, the spectrum range, where wind noise
has an energy i.e. below 10
4 Hz is exactly that range where a hearing device should be effective, because individuals
have often impaired hearing abilities in this range. Attenuating wind noise with a
static high-pass filter will either filter too little of the wind noise to maintain
normal signal perception, or to such an amount that wind noise is well cancelled,
but also normal acoustical signals to be perceived. Switching beamforming off as proposed
in the above mentioned documents significantly reduces the overall advantages of a
hearing device with beamforming abilities also at higher frequencies.
[0009] It is an object of the present invention generically to provide methods and devices
which deal with the above mentioned drawbacks. Although it departs from the specific
wind noise problems, some of the solutions according to the present invention may
also be applied for improving signal-to-noise ratio more generically with respect
to normal acoustical signals as of speech or music signals or for improving beamformer
control and/or wind detection.
[0010] Detailed theoretical considerations to the different aspects of the present invention
may be found in the paper from F. Pfisterer for achieving their diploma at the Federal
Institute of Technology in Zurich. Because this paper was not published when filing
the original of the parent application and discloses more details which might interest
the skilled artisan, this paper was enclosed to the original description as an Appendix
and as an integral part of the description. This paper is now published as:
Franziska B. Pfisterer: Wind Noise Cancelling for Hearing Instruments, Diploma Thesis
dip/7406, Signal and Information Processing Laboratory, Swiss Federal Institute of
Technology Zurich, Winter Semester 2002/2003; List of the Master (& Diploma) Theses
completed in the last few years (at the Signal and Information Processing Laboratory,
Swiss Federal Institute of Technology Zurich). The document is only available at the
library of the addressed institute,
http://www.isi.ee.ethz.ch/research/master-theses.
1st Aspect
[0011] Under a first aspect of the present invention the above mentioned object is resolved
by manufacturing a specifically tailored hearing device. There is proposed a method
for manufacturing such a hearing device which comprises the steps of
- providing in a hearing device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing an audio signal processing unit for establishing audio signal processing
of the device according to individuals' needs and/or purposes of the device, having
an input and an output;
- providing at least one electrical/mechanical output converter with an input;
- providing a filter arrangement with adjustable high-pass characteristic and with a
control input for the characteristic, further having an input and an output, and
- establishing the following operational connections:
between the output of the input converter arrangement and the input of the filter
arrangement,
between the output of the filter arrangement and the control input,
between the output of the filter arrangement and the input of the processing unit,
between the output of the processing unit and the input of said at least one output
converter.
[0012] Thereby, establishing the operational connections as mentioned needs clearly not
be performed in a time sequence according the sequence of above wording. The operational
connections may at least in part be established between units before they are assembled.
Further, it must be emphasized that the output signal of the filter arrangement is
just an improved "picture" of the acoustical signals, specific signal processing as
for hearing aid devices is performed downstream the filter arrangement.
[0013] By this method there is provided a hearing device at which the high-pass characteristic
is adapted to the acoustical situation.
[0014] In a most preferred embodiment of this method, the step of establishing operational
connection of the output of the filter arrangement to the control input of the high-pass
filter is performed via a statistics evaluating unit.
Definition
[0015] By the term
"statistics evaluation unit" we understand a unit at which the behavior of the input signal is continuously monitored
during a predetermined amount of time and there is formed over time a statistical
criterion of such signal. Generically the output signal of the statistic-forming unit
reacts with a time lag on momentarily prevailing characteristics of the input signal
and has thus, generalized, a low-pass characteristic. In fact and as example such
statistics-forming and evaluating unit may include LMS-type algorithms (Least Means
Square) or other algorithms like Recursive Least Square (RLS) or Normalized Least
Means Square (NLMS) algorithms.
[0016] In a proposed preferred embodiment the statistics-evaluating unit as provided determines
the amount of energy of the signal fed to its input and being indicative of the energy
at the output of the filter arrangement. Adjusting the high-pass filter characteristic
is performed so as to minimize such energy. Thereby preferably one of the algorithms
mentioned above is applied. By adjusting the high-pass characteristic, the cut-off
frequency or frequencies and/or attenuation slope or slopes and/or low frequency attenuation
may be adjustable. In a further embodiment the statistics forming and evaluation unit
may estimate speech intelligibility of the output signal of the filter arrangement
e.g. by computing the known speech intelligibility index or may estimate speech quality
e.g. by computing segmental SNR.
[0017] In a far preferred embodiment of this method of manufacturing a hearing device the
addressed high-pass filter arrangement is realized with a predictor unit, thereby
preferably in that there is operationally connected to the output of the input converter
arrangement a unit with a predictor unit in the following structure:
- an adjustable low-pass filter is provided with an input operationally connected to
the output of the input converter arrangement and with an output operationally connected
to one input of a comparing unit;
- there is operationally connected the output of the input converter arrangement substantially
unfiltered with respect to frequency to a second input of the comparing unit;
- finally the output of the comparing unit is operationally connected to a control input
of the low-pass filter for adjusting the characteristic of the low-pass filter. The
control input of the low-pass filter establishes the control input of the high-pass
filter arrangement, the output of the comparing unit is in fact the output of the
high-pass filter arrangement.
[0018] In fact by means of the low-pass filter - with a preceding delay unit - there is
established prediction of evolution of the filter input signal. By comparing the output
signal of the low-pass filter with the instantaneously prevailing unfiltered signal,
principally as occurring at the output of the input converter arrangement, there results
a prediction difference between actual signal and predicted signal. As in a most preferred
embodiment the low-pass filter is controlled from the output of the comparing unit
via statistics evaluation unit, thus with a relatively long reaction time, the low-pass
filter may be adjusted to minimize the difference of prediction and actual signal,
nevertheless substantially maintaining the spectrum of acoustical normal signals as
of speech and music substantially less attenuated. By means of high-pass filter characteristic
adjustment the device manufactured becomes optimally adapted to time-varying wind
situations.
[0019] In a further most preferred embodiment which is especially applied in combination
with the above mentioned predictor technique there is provided an analog to digital
conversion unit, which is operationally connected at its input side to the output
of the input converter arrangement and operationally connected at its output side
to the input of the addressed high-pass filter arrangement. Thereby, the said filter
arrangement is construed as a digital filter arrangement.
[0020] A hearing device, which resolves the above mentioned object comprises a processor
unit for establishing signal processing of the device according to individual needs
and/or purpose of the device and has an input and an output. There is further provided
at least one, for binaural devices two output electrical/mechanical converters with
an output; further there is provided an acoustical/electrical input converter arrangement,
a filter arrangement with adjustable high-pass characteristics. The input of the filter
arrangement is operationally connected to an output of the input converter arrangement,
which has a control input for adjusting the characteristic. The control input is operationally
connected to the output of the filter arrangement, which is further operationally
connected to the output converter via the processing unit.
[0021] Further preferred embodiments of such device are disclosed in the claims and the
detailed description.
[0022] Under the first aspect of the present invention the above mentioned object is resolved
by the method of reducing disturbances, especially wind disturbances, in a hearing
device with an input acoustical/electrical converter arrangement, which generates
a first electric output signal. Such method comprises the steps of filtering a signal
which is dependent from the first electric signal with a variable high-pass characteristic
so as to generate a second electric signal and by adjusting the variable characteristic
of the high-pass filter by a third signal which is derived or dependent on the second
signal. In a preferred mode generating the third signal in dependency of the second
signal, includes performing a statistical evaluation on the second signal, and the
third signal is generated in dependency of the result of the statistical evaluation.
Thereby, in a still further preferred embodiment the energy of the second signal is
evaluated and adjusting of the high-pass characteristic is performed so as to minimize
this energy.
[0023] In a most preferred embodiment filtering is realized by predicting and forming a
difference from a prediction result and an actual signal, whereby such difference
is minimized by appropriately adjusting the filter characteristics. Further, in a
preferred form of realizing the method it comprises the steps of
- low-pass filtering a signal dependent on the output signal of the input converter
arrangement with an adjustable low-pass characteristic;
- comparing a signal dependent on the result of the low-pass filtering with a signal
dependent from the output of the input converter substantially unfiltered with respect
to its frequency content, and
- controlling the adjustable high-pass characteristic by controlling the adjustable
low-pass characteristic.
[0024] Most preferably and especially in the last mentioned realization form, filtering
and adjusting is performed digitally.
[0025] By the methods and the device according to the present invention under its first
aspect as outlined above, irrespective whether an input acoustical/electrical converter
arrangement has one or more than one acoustical/electrical input converters, wind
noise is substantially canceled adaptively to the prevailing wind noise situation.
Thereby, the signal components to be perceived as resulting from speech or music are
substantially less attenuated than wind noise components. Whenever statistic forming
and evaluation is performed on basis of a correlation, in a preferred embodiment the
statistics forming and evaluation unit has a further input which is operationally
connected to the input of the filter arrangement.
2nd Aspect
[0026] Under a second aspect the present invention deals most generically with improving
signal-to-noise ratio at a hearing device. Thereby, and as will be explained under
this second aspect this part of the invention is most suited to reestablish improved
signal-to-noise ratio with respect to wind noise after a signal has been processed
by high-pass filtering as was explained under the first aspect of the invention.
1st sub-aspect
Definition:
[0027] We understand under a "pitch" spectral peaks or peaks of narrow band-width. The fundamental
and the spectral harmonics of a signal represent such "pitches".
[0028] A pitch-filter is comb-filter with a multitude of narrow pass-bands. It covers for
a signal with fundamental and harmonic spectral lines all predominant lines or a predetermined
number thereof with pass-bands.
[0029] Under a first sub-aspect of the present invention there is provided a method for
manufacturing a hearing device, which comprises the steps of
- providing in a hearing device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing a pitch filter with adjustable pitch position and with a control input for
the pitch position and further with an input and with an output;
- providing a pitch detector arrangement with an input and with an output, and
- establishing operational connection between the electric output of the input converter
arrangement and the input of the pitch filter and between the output of the input
converter arrangement and the input of the pitch detector arrangement, and further
between the output of the pitch detector arrangement and the control input at the
pitch filter.
[0031] Generically by means of the pitch detector discrete frequency components in the signals
output from the input converter arrangement are detected and their specific frequencies
monitored. By controlling pitch position of the pitch filter, i.e. spectral position
of its pass-bands, to track the frequencies as monitored, SNR of pitches to noise
in the processed signal is improved. Thereby, such pitch signal components are amplified
relative to the spectrally intermediate noise.
[0032] It has to be emphasized again that establishing the operational connection in the
method of manufacturing the hearing device with the pitch filter may be done at least
in part well in advance of assembling the units to form the device whenever pitch
detection is to be performed by a recursive method, in a preferred embodiment a further
input of the pitch detector is operationally connected to the output of the pitch
filter.
[0033] Under this first sub-aspect there is further provided a hearing device, which comprises
- an acoustical/electrical input converter arrangement with an output;
- a pitch filter with adjustable pitch position and a control input for said pitch position,
further having an input and an output;
- a pitch detector unit with an input and with an output, whereby the output of the
input converter arrangement is operationally connected to the input of the pitch filter,
the output of the input converter arrangement is further operationally connected to
the input of the pitch detector unit, and the output of the pitch detector unit is
operationally connected to the control input at the pitch filter.
[0034] There is further provided a method for improving signal-to-noise ratio in a hearing
device, which comprises pitch filtering a first signal dependent from an output signal
of an acoustical/electrical input converter arrangement, monitoring the actual pitch
frequencies of predominant frequency components within the first signal and adjusting
the pitch position of the pitch filtering dependent on the actual pitch frequency
positions as monitored.
[0035] As was already mentioned above, by the technique according to the present invention
under its first aspect the signal components to be improved as resulting from speech
or music may be attenuated to some extent by high-pass filtering. By combining the
present invention under the just addressed 1st sub-aspects with the invention according
to the first aspect SNR with respect to wind noise is further improved. This is realized
by first operating or performing the invention with adjustable high-pass filtering
upon a signal dependent from the output signal of the input converter arrangement
and operating on a signal dependent on the output signal of such high-pass filtering
the technique according to the just addressed 1
st sub-aspect, namely of pitch filtering with controllably adjustable pitch frequency
position.
2nd sub-aspect
[0036] Under the second aspect of the present invention and thereby under a second sub-aspect
thereof there is provided improved SNR ratio especially with respect to speech signals.
[0037] With respect to spectrum, one characteristic of speech signals is that the fundamental
is approximately between 50 Hz and 1 kHz.
[0038] Under this second sub-aspect there is provided a method for manufacturing a hearing
device comprising:
- providing in a hearing device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing an adding unit with at least two inputs;
- providing a first band pass filter unit with an input and with an output and with
a band selected to pass selected harmonics of speech;
- a non-linear modulation unit with an input and with an output;
- a second band pass filter unit or a low-pass filter unit with an input and with an
output and with a pass-band selected on a different harmonics of speech,
and establishing the following operational connections:
from the output of the input converter arrangement to one input of the adding unit
without substantial frequency filtering;
from the output of the input converter arrangement to the input of the first band
pass filter unit without substantial frequency filtering;
from the output of the first band pass filter unit to the input of the non-linear
modulation unit and from the output of the non-linear modulation unit to the input
of the second band pass or low-pass filter unit and finally from the output of the
second band pass or low-pass filter unit to the second input of the adding unit.
[0039] By manufacturing a hearing device as stated the following is realized:
On the output signal of the input converter arrangement speech signals shall be present
also and especially with their fundamental components. Due to band-restricted noise
as e.g. and especially wind noise, SNR greatly varies considered along the pitches
of speech. By selecting at the first band pass filter unit a pass-band according to
a harmonics of speech at which a good SNR prevails and
subjecting such band filtered signal to a non-linear modulation, all harmonics are
regenerated with good SNR.
From all the harmonics generated by the non-linear modulation one or more than one
band is selected by respective one or more than one second band pass filters or
a low-pass filter. The resulting, remaining selected harmonics may first be amplified
if desired and are added to the original fundamental and/or harmonics. Thus, in the
resulting signal pitches of speech with originally low SNR are improved with respect
to that SNR.
[0040] In a preferred mode of the manufacturing method under this second sub-aspect, an
analog to digital conversion unit is provided with an input and with an output, and
there is established the operational connection between the output of the input converter
arrangement and the one input of the adding unit as well as to the input of the first
band pass filter via such analog to digital conversion unit. Thereby, the filter units,
the non-linear modulation unit and the adding unit are realized as digital units.
[0041] Still under the second sub-aspect of the second aspect of the present invention there
is further proposed a hearing device which comprises an acoustical/electrical input
converter arrangement with an output, a first band pass filter unit with an input
and with an output and with a band selected to pass selected harmonics of speech,
a non-linear modulation unit with an input and with an output, a second band-pass
filter or low-pass filter unit selected to pass different selected harmonics having
an input and an output. There is further provided an adding unit with two inputs and
with an output. The output of the input converter arrangement is operationally connected
to a first input of the adding unit, substantially without frequency filtering, the
output of the input converter arrangement is further operationally connected to the
input of the first band pass filter unit, whereby the output of that unit is operationally
connected to the input of the non-linear modulation unit. The output of the non-linear
modulation unit is operationally connected to the input of the second band pass filter
or of the low-pass filter unit, the output of which being operationally connected
to the second input of the adding unit.
[0042] Again, preferred embodiment of that device are disclosed in the claims and the specific
description.
[0043] Under this second sub-aspect there is further proposed a method for increasing signal-to-noise
ratio at a hearing device and especially with respect to speech signals with an acoustical/electrical
input converter generating a first electric signal, which comprises the steps of
- band pass filtering a signal dependent on said first signal to generate a band pass
filtered signal with harmonic components of speech;
- modulating said filtered signal at a non-linear characteristic to generate an output
signal with a re-increased number of harmonic components of speech;
- band- or low-pass filtering said output signal with said re-increased number of harmonic
components to generate a further signal with selected harmonic components and superposing
said further signal to a signal dependent on said first electric signal.
[0044] Again the techniques according to this second sub-aspect of the present invention
are ideally suited to be combined with the technique as taught under the first aspect
of the present invention as disclosed in the claims and the detailed description.
3rd aspect
[0045] As was mentioned above prior art electronic approaches to quit with wind noise at
hearing devices with beamforming ability disable such ability whenever wind noise
is too large.
[0046] Under the third aspect of the present invention a technique is proposed on one hand
to substantially cancel wind noise and on the other hand to substantially maintain
beamforming ability.
[0047] According to the invention under the third aspect there is proposed a method of manufacturing
an acoustical device, especially a hearing device, which comprises the steps of providing
in a device casing an acoustical/electrical input converter arrangement generating
at an output an electrical signal in frequency or frequency band domain with a beamformer
amplification characteristic of acoustical signals impinging on said arrangement in
dependency of impinging angle with which the acoustical signals impinge thereon and
with a predetermined frequency roll-off characteristic of the beamformer characteristic.
[0048] There is further provided a normalizing unit with in input and with an output and
there is established an operational connection of the output of the converter arrangement
and the input of the normalizing unit. Further, there is provided a memory unit with
the predetermined roll-off characteristic stored therein. Still further, there is
provided a comparing unit.
[0049] There is established an operational connection between the output of the normalizing
unit and one input of the comparing unit as well as between the output of the storing
unit and the second input of the comparing unit.
[0050] There is additionally provided a controlled selection unit with a control input,
an input as well as an output and there is established an operational connection between
the output of the converter arrangement and the input of the selection unit as well
as between the output of the comparing unit and the control input of the selection
unit. The selection unit is controlled to attenuate frequency components of the electric
signal input to its output, the normalized values of which non-resulting in a predetermined
comparison result at the comparing unit differently than such components for which
said comparison does result in the predetermined result.
[0051] Although it is absolutely possible to provide an acoustical/electrical input converter
arrangement with a single acoustical/electrical input converter as of a directional
microphone with an intrinsic beamformer characteristic, also in this case it is preferred
to provide at the input converter arrangement at least one second acoustical/electrical
input converter.
[0052] This is clearly also the case if the beamformer characteristic is generated, as known,
on the basis of the output signals of two or more than two distinct acoustical/electrical
converters.
[0053] Therefore, in a most preferred embodiment of this method, the input converter arrangement
as provided has at least two input acoustical/electrical converters.
[0054] Whenever an input converter arrangement is provided with at least two acoustical/electrical
converters, in a most preferred embodiment the input arrangement is provided with
at least two time domain to frequency or to frequency band domain conversion units.
One of these conversion units is operationally connected to one of the at least two
input converters, the second one of these conversion units to a second one of the
at least two input converters. Thereby, in fact before beamforming-processing of the
output signals of the at least two input converters, the output signals of these input
converters are time domain to frequency or frequency band domain converted.
[0055] On the other hand whenever beamforming is performed intrinsically by an input converter
with directional characteristic, the output signal of that converter as well as the
output signal of a further input converter is time domain to frequency or frequency
band domain converted.
[0056] In a further preferred embodiment there is provided the beamformer unit with a control
input and there is established an operational connection between the output of the
comparing unit and the control input of the beamformer unit.
[0057] By establishing an operational control connection between the output of the comparing
unit and a control input of the beamformer unit it becomes possible to selectively
control the beamforming ability of the beamformer unit according to evaluation of
the comparing results as mentioned above.
[0058] Further, in a preferred embodiment and whenever the input converter arrangement as
provided has at least two input acoustical/electrical converters there is established
an operational connection between an output of one of these at least two input converters
via a further output of the input converter arrangement, and a further input of the
normalizing unit for receiving there a normalizing signal.
[0059] In a further preferred mode thereof there is interconnected between the output of
the said one input converter the further input of the normalizing unit, a time domain
to frequency or frequency band domain conversion unit, so that the normalizing signal
applied to the further input of the normalizing unit is in frequency or frequency
band domain. Thus, normalizing signals are applied frequency- or frequency band-specifically.
[0060] In a further preferred mode, varying attenuation at the selection unit is performed
softly. It is preferred not to binaurally switch from maximum attenuation, e.g. leading
to zero level, to minimum attenuation e.g. leading to maximum level. Therefore, in
a further preferred embodiment there is provided a signal transfer unit with a low-pass-type
signal transfer between its input and output, and the operational connection between
the output of the comparing unit and the control input of the selection unit is provided
via such signal transfer unit. At the selection unit, preferably, frequency or frequency
band-specific attenuation is adjustable continuously of substantially continuously
as in small steps, controlled by the control signals.
[0061] In a most preferred embodiment for manufacturing a hearing device at which wind noise
is optimally canceled the predetermined result established is when said normalized
values are at most equal to roll-off characteristic values at the respective frequencies
considered. There is thus checked, whether the normalized beamformer output signals
at the specific frequency is at most equal to the value of the roll-off characteristic
at that frequency, and if it is this frequency component is passed to the output by
the selection unit, if it is not the respective component becomes attenuated.
[0062] Accordingly there is provided under this third aspect of the invention, an acoustical,
thereby especially a hearing device which comprises an input acoustical/electrical
converter arrangement, which has an output and generates an output signal thereat
with a beamformer amplification characteristic having a predetermined frequency roll-off
characteristic. This output signal is in the frequency or in the frequency band domain.
There is further provided a normalizing unit with an input which is operationally
connected to the output of the input converter arrangement and with an output which
is operationally connected to one input of a comparing unit. There is further provided
a memory unit with a predetermined roll-off characteristic stored therein, an output
of which being operationally connected to a second input of the comparing unit. A
control selection unit with a control input and a signal input operationally connected
to the output of the input converter arrangement has its control input operationally
connected to the output of the comparing unit, thereby controllably attenuating frequency
components in a signal input to a signal output, for which comparison has not shown
up a predetermined result, thereby performing said attenuating differently than upon
components for which the comparison result has affirmatively resulted in the predetermined
result.
[0063] Preferred embodiments of such device are disclosed in the claims as well as in the
detailed description.
[0064] Under this third aspect there is further provided a method for at least substantially
canceling wind disturbances in an acoustical device, thereby especially in a hearing
device, which has an input acoustical/electrical converter arrangement, which generates
at an output an electric signal in frequency or in frequency band domain with a beamformer
amplification characteristic with respect to impinging angle with which acoustical
signals impinge upon the arrangement and with a predetermined frequency roll-off characteristic.
The method comprises the steps of normalizing a signal which depends on the electric
signal in frequency or frequency band domain, comparing frequency or frequency band
specifically the normalized signals with respective values of the frequency roll-off
characteristic and attenuating frequency signal components of the electrical signal
in dependency of the results of the comparing operation.
[0065] Here too, preferred embodiments of this method are disclosed in the claims as well
as in the detailed description.
4th aspect
[0066] As was mentioned above in prior art attempts wind noise canceling was established
in hearing devices with beamforming abilities just by switching off such beamformer
ability and going on by processing acoustical signals substantially based on an omnidirectional
characteristic.
[0067] Under the present fourth aspect an approach has been invented, according to which
the beamformer ability is only attenuated up to complete switch off at those frequencies
or frequency bands, where significant disturbances are present. More generically,
nevertheless departing from the above mentioned wind noise canceling problem, a technique
is proposed, by which beamforming abilities at an acoustical device may frequency
or frequency band selectively be reduced up to switching such beamforming ability
off.
[0068] A method of manufacturing a beamforming device, thereby especially an acoustical
device and even more specifically a hearing device, comprises providing in a casing
of the device a beamformer unit which operates in frequency or in frequency band domain.
At such beamformer unit there is provided a control input, which frequency or frequency
band selectively controls beamforming of the beamformer unit. There is further provided
a control unit which has an output for frequency or frequency band selective control
signals, and there is established an operational connection between the output of
the control unit and the said control input.
[0069] With an eye on specific noise canceling purposes the method comprises providing the
control unit with a frequency or frequency band selective noise detector.
[0070] Thereby, with an eye on wind noise handling, the control unit is provided having
a wind noise detector. Thereby, it must be established that wind noise is in fact
a band-specific noise, which is detected by a respectively tailored frequency- or
frequency band-selective noise detector.
[0071] In a most preferred mode there is provided the beamformer unit with at least two
input converters, each having an output. There is further provided at least one controlled
frequency- or frequency band-specific attenuation unit with a frequency or frequency
band selective attenuation control input, further with an input and an output. For
beamforming there is further provided a beamformer processing unit, which has at least
two inputs and an output.
[0072] Operational connections are established between an output of one input converter
via the attenuation unit to one input of the processing unit. Thereby, clearly both
outputs of the at least two input converters may be operationally connected to the
inputs of the processing unit via such an attenuation unit.
[0073] In any case there is established an operational connection between the output of
a second input converter and the second input of the processing unit. Further, an
operational connection is established between the output of the control unit and the
control input of the attenuation unit.
[0074] Under this fourth aspect of the present invention there is further proposed a beamforming
device, preferably an acoustical device, most preferably a hearing device, which comprises
a beamformer unit, which is operating in frequency or frequency band domain, and which
has a control input for frequency or frequency band selectively controlling beamforming.
There is further provided a control unit, which has an output for frequency- or frequency
band-specific control signals, which is operationally connected to the said control
input.
[0075] Preferred embodiments of such method and device are disclosed in the claims as well
as in the detailed description.
[0076] Still under the fourth aspect of the present invention it is proposed a method for
controlling beamforming - especially for acoustical appliances, thereby most preferably
for hearing device appliances - which method comprises performing beamforming in frequency
or frequency band domain and controlling beamforming frequency- or frequency band-selectively.
[0077] Again preferred embodiments of this method are disclosed in the claims as well as
in the detailed description.
[0078] The invention under the presently discussed fourth aspect, namely of selectively
controlling beamforming, may and is preferably used and applied when realizing the
present invention under its third aspect:
[0079] According to the third aspect, spectral components of a signal are determined and
selected (comparison with roll-off characteristic) which are more noise disturbed
than others. Once such selection has been made, the same selection may be applied
to the presently proposed frequency or frequency band selective attenuation of beamforming.
In such a combination not only that selected frequency of frequency band components
are attenuated with a preferred slowly varying attenuation, but additionally beamforming
in frequencies or frequency bands of those components is, preferably steadily or slowly,
attenuated, resulting finally and for those specific frequency or frequency bands
considered, in beamforming being switched off, thereby transiting to omnidirectional
amplification characteristic for those frequencies or frequency bands.
5th aspect
[0080] As the skilled artisan is perfectly aware of, it is a need in acoustical devices
and especially hearing devices to detect whether wind noise is present to a higher
amount than desired so as to take appropriate measures in controlling such device.
This is true for such devices irrespective whether their input acoustical/electrical
converter arrangement is based on acoustical signal reception by means of one single
acoustical/electrical input converter or by means of more than one such input converters,
as for two or more converter beamforming.
[0081] Under this fifth aspect the present invention proposes a novel and most advantageous
wind noise detection technique, which may be applied especially irrespective of the
concept of the input converter arrangement with respect to number of acoustical/electrical
converters.
[0082] This object is resolved by a method of manufacturing an acoustical device, which
comprises providing an acoustical/electrical input converter arrangement into a casing
of the device, whereby the arrangement has an output. There is further provided a
calculation unit, which has an input and an output. Operational connection is established
between the output of the converter arrangement and the input of the calculating unit.
[0083] The calculation unit is programmed to calculate from a signal input the frequency
coordinate values of the balance point of a surface defined by the spectrum of the
said signal in a predetermined frequency range. The calculating unit thereby generates
an output signal in dependency of the said coordinate value, which is indicative of
wind noise.
[0084] In a most preferred embodiment the calculation unit as provided is programmed to
continuously average the coordinate values of the addressed balance point over a predetermined
amount of time and/or to continuously calculate the variance of the coordinate value
over a predetermined amount of time. Thereby, preferably generating of the output
signal comprises generating such signal at least in dependency of such averaging and/or
the said variance.
[0085] Preferred embodiments of this method are disclosed in the claims as well as in the
detailed description.
[0086] Under this fifth aspect of the invention there is further proposed an acoustical
device, which comprises an acoustical/electrical input converter arrangement with
an output, a calculation unit with an input being operationally connected to the output
of the converter arrangement. The calculation unit is programmed to calculate from
an input signal the frequency coordinate value of the balance point of a surface of
the spectrum in a predetermined frequency range. The calculation unit further generates
an output signal in dependency of the found coordinate value, which output signal
is indicative of wind noise.
[0087] Preferred embodiments of this device are disclosed in the claims as well as in the
detailed description.
[0088] There is further proposed under this fifth aspect of the present invention a method
of detecting wind noise at an acoustical device with acoustical/electrical conversion
to generate an electric signal. Such method comprises the step of electronically calculating
the frequency coordinate value of the balance point of the spectrum of the signal
within a predetermined frequency range and generating a wind noise indicative signal
in dependency of this value.
[0089] Preferred embodiments of this method are apparent to the skilled artisan from its
disclosure in the claims as well as the detailed description.
[0090] The invention shall now be described in more details and referring to examples and
with the help of figures.
[0091] The figures show by examples:
- Fig. 1
- wind spectra in dependency on wind direction;
- Fig. 2
- by means of a simplified schematic functional block/signal flow representation a hearing
device operating according to the method of reducing disturbances and manufactured
by a method, all according to the present invention under its first aspect;
- Fig. 3
- in a more detailed, but still simplified schematic functional block/signal-flow representation,
a preferred embodiment of the invention of fig. 2;
- Fig. 4
- in a simplified schematic functional block/signal- flow representation an acoustical
device which operates the method for improving signal-to-noise ratio and is manufactured
by a method, all according to the present invention under a first sub-aspect of a
second aspect;
- Fig. 5
- in a simplified schematic functional block/signal- flow representation a preferred
embodiment combining the invention under its first aspect and the invention under
the first sub-aspect of the second aspect;
- Fig. 6
- an acoustical device operating a method for increasing signal-to-noise ratio and manufactured
by a method all according to the present invention under a second sub-aspect of its
second aspect;
- Fig. 7
- simplified spectra for explaining functioning of the device and method as shown in
fig. 6;
- Fig. 8
- in a simplified functional block/signal-flow diagram a preferred combination of the
invention under its first aspect with the invention under the second sub-aspect of
its second aspect;
- Fig. 9
- by means of a simplified schematic functional block/signal-flow diagram an acoustical
device operating according the method for at least substantially canceling wind disturbances
and manufactured by a method, all according to the present invention under its third
aspect;
- Fig. 10
- as an example a roll-off characteristic (a), speech as well as wind spectra for explaining
the effect of the invention under its third aspect;
- Fig. 11
- by means of a simplified schematic functional block/signal-flow representation a preferred
input acoustical/electrical converter arrangement as preferably used in the embodiment
of fig. 9;
- Fig. 12
- by means of a simplified schematic functional block/signal-flow representation a preferred
embodiment of signal control as preferably applied to the invention as explained with
the help of figures 9 to 11;
- Fig. 13
- by means of a simplified schematic functional block/signal flow representation a beamforming
device operating the method for controlling beamforming and manufactured by a method,
all according to the present invention under its fourth aspect, and
- Fig. 14
- by means of a simplified functional block/signal- flow representation an acoustical
device operating to perform the method of detecting wind noise and manufactured by
a method, all according to the present invention under its fifth aspect.
[0092] In fig. 1 there is shown wind noise spectral characteristic for a wind speed of 10
m/s at an individual head with no hair. Therefrom it might be seen that wind noise
spectrum varies significantly as wind direction alters with respect to a device registering
such noise. Nevertheless, wind noise spectrum is band-limited.
[0093] In fig. 1 there is further schematically introduced the approximate frequency band
for human speech fundamental pitch.
1st aspect
[0094] In Fig. 2 there is shown, by means of a simplified schematic signal-flow/functional
block diagram, an acoustical device, especially a hearing device as manufactured according
to the present invention under its first aspect. The device as shown performs the
method according to the present invention under this first aspect.
[0095] The device comprises, assembled into a schematically shown device casing 1, an input
acoustical/electrical converter arrangement 3. Such arrangement 3 may comprise one
or more than one specific acoustical/electrical converters as of microphones. It provides
for an electric output at A
3, whereat the arrangement 3 generates an electric signal S
3-Possibly via some signal processing, as e.g. pre-filtering and amplifying (not shown),
a signal S
3' dependent on S
3 is fed to input E
5 of a high-pass filter arrangement 5. The filter arrangement 5 has a control input
C
5 for control signals SC
5 which, applied to C
5, control the high-pass characteristic as shown in block 5 and with respect to its
one or more than one corner frequencies f
c, its low-frequency attenuating, one or more than one attenuation slopes. The high-pass
filtered signal S
5 output at an output A
5 and is operationally connected, possibly via further signal processing, especially
as will be described in context with the second aspect of the present invention, to
one or more than one electrical/mechanical output converter arrangements 7 of the
device.
[0096] With an eye on manufacturing such device all the units as of 3, 5, 9, 7 will be assembled
in a casing, whereby they need not be all assembled in the same casing 1, wherein
the input converter arrangement 3 is provided. Further, the addressed operational
signal connection may be established during or after assembling of the device, some
or even all of them may nevertheless be preassembled as by combining units by an integration
technique.
[0097] A signal S
5" dependent on signal S
5 as output by high-pass filter unit 5, possibly made dependent via additional signal
processing as e.g. amplification, is fed from the output A
5 to an input E
9 of a unit 9, which most generically performs upon the signal S
5" a statistical evaluation. The statistic-forming unit 9 performs registering and
evaluating selected characteristics of signal S''
5 over time. There results from performing such statistical evaluation that the signal
S
9 has a low-pass-type dependency from signal S"
5 input to unit 9. The output signal S
9 at output A
9 is operationally connected, possibly by some intermediate additional signal processing,
as e.g. amplification or filtering, to the control input C
5 as a control signal SC
5 and controls the high-pass filter characteristic HP of filter unit 5. As shown in
fig. 2, whenever the improved audio signal as of S
5 has to be further processed so as to take individual hearing improvement needs into
account, so as customary for hearing aid devices, such processing is performed downstream
S
5 at a processor unit PR.
[0098] In spite of the fact that functioning of the most generic embodiment as of fig. 2
might be better understood when reading the following explanations to fig. 3 with
respect to a preferred form of realization, it is already clear from the embodiment
of fig. 2, that, with an eye on fig. 1, the high-pass filter arrangement 5 provides
for attenuating wind noise has its corner frequency f
c set and adjusted adjacent the upper end of the wind noise spectra, i.e. somewhere
between 1 kHz and 10 kHz. The unit 9 generates the output signal S
9 which does not vary in time on the basis of short-term single signal variation of
S"
5, but only with long-term or frequency variations and thereby controls the filter
characteristics of filter arrangement 5 to optimize attenuation of such long-term
or frequent variations, i.e. signal components as resulting from wind noise. Signal
components in S''
5 resulting from normal acoustical signals not to be canceled as from speech or music
and appearing in S"
5 with spectra rapidly changing in time will substantially not be canceled by the filter
arrangement 5, at least substantially less than steadily or slowly varying or repeatedly
occurring signal components as caused by wind noise.
[0099] In fig. 3 there is shown a most preferred form of realization of the device and method
as disclosed with the help of fig. 2 and accordingly of manufacturing a respectively
operated hearing device.
[0100] Thereby, signal processing is realized by digital signal processing. Functional blocks
and signals, which have already been explained in context with fig. 2 are shown in
fig. 3 with the same reference numbers. The output signal S
3 of input converter arrangement 3 is analog/digital converted by an analog/digital
conversion unit 11. The filter arrangement 5 as of fig. 2 is realized by a digital
filter unit 13. The signal S
3' as input according to fig. 2 to the filter arrangement 5 is now digital and applied
to the input E
13 of digital HP-filter unit 13. The high-pass - HP - filter arrangement 5 is realized
making use of a predictor 15. It comprises a time delay unit 19 and a low-pass digital
filter 17, which may be of FIR or IIR type and may be of any particular implementation,
e.g. of lattice, direct form, etc. structures.
[0101] Signal samples x(n) from input signal S'
3 are input to time delay unit 19, at its input E
19. Delayed samples x(n-1) at output A
19 of unit 19 are input at input E
17 to low-pass filter unit 17, whereat the samples are low-pass filtered to generate
at an output A
17 an output signal p(n). The units 19 and 17 represent as known to the skilled artisan
a predictor and the output signal p(n) is the prediction result.
[0102] The prediction result p(n) is compared by subtraction at a subtraction unit 21 with
the actual sample x(n) of the actual input signal according to S'
3. Thereby, the output A
17 of filter unit 17 is operationally connected to one input of comparing unit 21, the
other input thereof being operationally connected to the input E
13 of high-pass filter unit 13 without substantial frequency filtering. A matching time
delay unit may be introduced in the connection from input E
13 to the one input of unit 21 as shown in dashed lines at 22.
[0103] At the output A
21 of the comparing unit 21 the predictor error signal e(n) is generated, which is indicative
for the deviation of the prediction result p(n) from actual signal x(n).
[0104] The low-pass filter unit 17 has a control input C
17. A control signal applied to that input C
17 adjusts the coefficients and/or adaption time constants of the digital filter unit
17. The input C
17 of low-pass filter unit 17 represents, with an eye on fig. 2, the control input C
5 of the high-pass filter arrangement 5.
[0105] The signal S
13 according to the predictor error e(n), is on one hand and as was explained in context
with fig. 2 operationally connected to at least one electrical/mechanical output converter
(not shown here) of the device.
[0106] Further, a signal S
13", which depends, possibly via some additional signal processing as e.g. amplification,
to signal S
13 is input to input E
23 of statistics forming and evaluating unit 23. In a most preferred embodiment unit
23 monitors the overall energy of the signal S"
13. The control signal C
17 to the low-pass filter unit 17 is made dependent from the output signal S
23 of unit 23, which is representing the overall energy of the input signal S
13". Thereby, in fact in the sense of a negative feedback control loop via control input
C
17, the adaption time constants and/or the filter coefficients of filter unit 17 are
adjusted to minimize the energy of signal S"
13 and thus of S
13. Thereby, LMS type algorithms or other algorithms like Recursive Least Square (RLS)
or Normalized Least Means Square (NLMS) algorithms may be used. In a different embodiment
the unit 23 may estimate speech signal intelligibility at signal S
13" e.g. by computing from that signal speech an intelligibility index. In a still further
embodiment, unit 23 may estimate speech signal quality e.g. by segmental SNR computation.
[0107] If unit 23 performs evaluation of statistics based on a correlation, and as shown
in dotted line at CR in Fig. 3, the input E
13 may be operationally connected to a further input E
232 of statistics forming and evaluating unit 23.
[0108] Although the embodiment of fig. 3, as has been explained, operates in time domain,
the same principal may be realized in frequency domain.
[0109] As the filter unit 17 is adjusted to minimize the energy of e(n), the predictor 19,
17 will reconstitute the predictable parts of signal x(n) as accurately as possible.
Therefore, the prediction error e(n) will only contain non-predictable parts of signal
x(n). Because wind noise constitutes substantially predictable components of x(n)
and, in opposition, signals to be perceived as especially from speech or music, are
non-predictable parts of x(n), the wind noise components are canceled from the output
signal S
13, finally acting upon the output converter 7, whereas speech or music signals, as
non-predictable signals, are passed by S
13 to the converter 7.
[0110] Experiments have shown that the order of the digital filter 17 may be low, preferably
below 5
th order FIR. The resulting filter is thus cheap to implement and still very efficient.
Such low-order filter has additionally the advantage of allowing relatively fast adaption
times, thus enabling tracking fluctuations of wind noise accurately. Further, it has
been found that by the disclosed technique, especially according to fig. 3, wind noise
is substantially more attenuated than target signals like speech or music, thereby
improving comfort and signal-to-noise ratios.
[0111] The skilled artisan being taught the invention under the first aspect may find other
adaptive filter structure to realize the principal technique as disclosed.
2nd aspect
[0112] Under this second aspect of the present invention two techniques have been invented,
one generically improving signal-to-noise ratio at an acoustical device, especially
hearing device, the other one doing so especially with an eye on speech target signals.
As will be shown both techniques are considered per se and self-contained as inventions,
but are most preferably combined with the teaching under the first aspect of the invention
to further improve low-frequency target signals within a frequency band covered by
wind noise spectrum.
1st sub-aspect
[0113] Fig. 4 shows, by means of a simplified, schematic functional block/signal-flow diagram
an acoustical device, especially a hearing device as manufactured by the present invention,
thereby disclosing a hearing device according to the present invention, which performs
the signal processing method according to the present invention, namely under the
first sub-aspect of its second aspect.
[0114] According to fig. 4 an input acoustical/electrical converter arrangement 3, which
again may be equipped with one or more than one input acoustical/electrical converters
as of microphones, provides at its output A
3 the signal S
3.
[0115] A signal D
3 which is dependent from S
3, especially preferred dependent by having been processed by an arrangement as was
disclosed in context with figs. 2 and 3 and thus the first aspect of the present invention,
is input to a pitch filter unit 30.
[0116] The pitch filter unit 30 is a comb filter as schematically shown within the block
of unit 30 with a multitude of pass-bands PB. The filter characteristic of the pitch
filter unit 30 is adjustable by a control signal SC
30 applied to a control input C
30. Thereby, especially the spectral positions as of f
1, f
2... of the pass-bands PB are adjusted. A further signal dependent on the signal S
3, preferably with the same dependency as D
3, F
32, is input to an input E
32 of a pitch detector unit 32.
[0117] Whenever signal F
32 has pitch components as schematically shown at the frequencies f
s1..., f
s3 exceeding noise spectrum N the pitch detector unit 32 detects the pitch frequencies
f
sx and generates at its output A
32 an output signal G
32 which is indicative of spectral pitch position, i.e. of the pitch frequency f
sx of input signal F
32.
[0118] The output A
32 of pitch detector unit 32 is operationally connected to the control input C
30 so as to apply there the control signal SC
30 which is indicative of spectral pitch positions within signal F
32 and thus S
3.
[0119] At the adjustable pitch filter unit 30 the spectral positions of the pass-bands PB
are thereby adjusted to coincide with the spectral pitch position f
sx in signal F
32 and thus in signal S
3, so that at the output A
30 of the adjustable pitch filter unit 30 a signal S
30 is generated, whereat the noise spectrum according to N is substantially attenuated,
whereas the pitch components are passed.
[0120] If the pitch detector unit 32 operates on the basis of a recursive detection technique,
a further input E
322 of unit 32 is operationally connected to the output A
30 of pitch filter unit 30.
[0121] This is shown in Fig. 4 by dashed lines at RC.
[0122] As not shown in fig. 4 again the output signal S
30 is further processed by the device specific signal processor, especially to consider
individual needs with respect to hearing improvement as was addressed in context with
fig. 2 and is finally operationally connected via such possible signal processing
to at least one output electrical/mechanical converter 7.
[0123] By the technique under this sub-aspect, signal-to-noise ratio of the device is significantly
improved.
[0124] Again with an eye on the method for manufacturing such a device, establishing operational
connections between the respective units may at least to a certain extent be done
before assembling such units to the one or more than one device casings, one of them
being schematically shown in fig. 1 at reference No. 1.
[0125] The teaching according to this sub-aspect of the present invention may ideally be
combined with the teaching of the present invention under its first aspect. This is
schematically shown in fig. 5. Thereby, the output A
3 of the input converter arrangement 3 is operationally connected, again preferably
via an analog to digital conversion unit (not shown), to the input E
5 of filter arrangement 5, preferably realized according to fig. 3, the output thereof,
A
5, being operationally connected to the adjustable pitch filter system 30/32 as of
fig. 4. Thereby, the pitch filter unit 30 in a preferred mode of realization will
especially be tailored with pass-bands within the wind noise spectrum as of fig. 1,
thereby to reestablish pitches, i.e. frequency components of the tracking signals
especially of speech or music signals in that spectral band.
[0126] Nevertheless, the technique according to this sub-aspect, i.e. applying a controllably
adjustable pitch filter, may be more generically used to reduce signal-to-noise ratio
with respect to tracking signals especially at acoustical devices.
2nd sub-aspect
[0127] The teaching according to this second sub-aspect is more specifically directed on
improving speech signals.
[0128] According to fig. 6 an input acoustical/electrical converter arrangement 3 has an
output A
3. A signal H
3 which depends from the signal S
3 output from input converter arrangement 3 is fed to a first input E
401 of an adding unit 40. At a point P along signal transfer path between S
3 and H
3 a signal I
3 is branched off. The operational connection of the output A
3 to the branching point P is thereby, in a preferred mode, established via the high-pass
filtering unit as was explained with the help of figs. 2 and 3 and in context with
the first aspect of the present invention as will be explained later. With respect
to frequency content there occurs substantially no frequency filtering in the signal
transfer path between branching point P and E
401, which would be different from such filtering of signal I
3. The signal I
3 is input to an input E
42 of a band-pass filter unit 42 with a pass-band PB
42. At the output A
42 of band-pass unit 42 an output signal I
42 is operationally connected to an input E
49 of a non-linear modulation unit 44.
[0129] At unit 44 the input signal I'
42 is modulated at a nonlinear e.g. parabolic characteristic. The modulation result
signal I
44 at output A
44 is operationally connected to input E
46 of a second band-pass filter or of a low-pass filter unit 46, without significant
frequency filtering.
[0130] Unit 46 generates at its output A
46 a signal I
46. A signal I'
46 dependent from the signal I
46 without significant frequency filtering is applied to the second input E
402 of adding unit 40, generating at its output A
40 the signal S
40. This output signal S
40 is (not shown) operationally connected to further signal processing units of the
acoustical device, especially the hearing device, which accomplishes device-specific
and/or user-specific signal processing.
[0131] The functioning of the device or method as shown in fig. 6 and thereby specific selection
of the filtering characteristics, especially of units 42 and 46, shall be explained
with the help of fig. 7.
[0132] In fig. 7(a) there is schematically shown on one hand wind noise spectrum N and on
the other hand the fundamental of a speech signal and its harmonics 1, 2, 3, ....
It may be seen that whereas fundamental and lower harmonics have bad SNR, higher harmonics
have increasingly better SNR.
[0133] According to fig. 7(b) the pass-band PB
42 of unit 42 is selected to pass high SNR harmonics, resulting in I
42 as of fig. 7(c).
[0134] This signal is subjected at unit 44 to non-linear modulation. As perfectly known
to the skilled artisan by such non-linear modulation, e.g. at a parabolic characteristic,
new harmonics are produced as generically shown in fig. 7(d), also considering intermodulation
products and folding at the zero-frequency axes.
[0135] It has to be noted that these harmonics are spectrally located exactly there where
the harmonics and fundamental of the original speech signal according to fig. 7(a)
are located.
[0136] The signal I
44 with good SNR or the signal dependent therefrom is fed to unit 46 with a filter characteristic
as shown in fig. 7(e), whereat those harmonics within signal I
44 according to fig. 7(d) are canceled or filtered out, which do not accord with original
speech harmonics according to fig. 7(a) to be improved as shown in fig. 7(e). At adding
unit 40 the signal I'
46 with the spectrum according to 7(f) possibly amplified is added to the signal H
3 with a spectrum according to fig. 7(a) resulting in an output signal S
40 with speech fundamental and lower harmonics significantly improved with respect to
SNR, and as shown in Fig. 7(g).
[0137] Thus, the pass-band PB 42 of unit 42 is selected to coincide spectrally with a harmonics
of speech with relatively good SNR and the characteristic of filter unit46 is selected
so that in the resulting signal harmonics are present, which coincide spectrally with
the poor SNR fundamental and lower harmonics of speech to be improved with respect
to SNR.
[0138] The embodiment as shown in fig. 6 may thereby be implemented digitally by providing
down-stream A
3 (not shown) an analog to digital conversion unit and further may be implemented by
signal processing in frequency or frequency band domain, thereby adding respective
time domain to frequency or frequency band domain conversion units.
[0139] As further shown in Fig. 6 a delay unit 43 may be provided between point P and input
E
401 to compensate for time delays between P and E
402.
[0140] With an eye on the method of manufacturing a device according to fig. 6 with a device
casing 1, the remaining units are provided and assembled in the same casing or in
different casings, the operational connections between the different units being established
before, at or after assembling the units in the one or more than one casings.
[0141] In a most preferred form the technique as disclosed with figs. 6 and 7 is combined
with upstream high-pass filtering of the output signals of the input converter arrangement
3, thereby especially preferred with adjustable high-pass filtering as was explained
with the help of the figs. 1 and 2 and which accords to the present invention under
its first aspect.
[0142] This is schematically shown in fig. 8. The system according to this fig. 8 needs
not be additionally described, besides of the fact that the system according to fig.
6 between branching point P and output signal S
40 is considered residing in unit 50.
3rd aspect
[0143] Under all the aspects of the present invention discussed up to now the addressed
input acoustical/electrical converter arrangement may comprise one or more than one
distinct input acoustical/electrical converters as of microphones and may thereby
provide for beamformer characteristics. Nevertheless, the arrangement may also comprise
only one distinct acoustical/electrical input converter.
[0144] In contrary thereto, the present invention under its third aspect is directed on
acoustical devices, especially hearing devices with a mores specific input converter
arrangement.
[0145] According to fig. 9 there is provided an input acoustical/electrical converter arrangement
60 with an output A
60 generating there an output signal S
60. The input converter arrangement 60 has the following characteristics:
- a) It provides for a beamformer amplification characteristics BF, i.e. with a specific
amplification characteristic of acoustical input signals ACU to electric output signal
S60 in dependency of direction of arrival ϕ with which such acoustical signals ACU impinge
on a sensing area of the arrangement 60.
- b) The beamformer characteristic of amplification has a predetermined roll-off characteristic
RO. This roll-off characteristic defines for a considered DOA angle ϕ, how the amplification
is attenuated as a function of signal frequency. Such a roll-off characteristic over
frequency is shown in fig. 10 by course (a).
- c) Further, within the input converter arrangement 60 analog to digital conversion
as well as time domain to frequency or frequency band domain conversion is performed.
[0146] Such beamformer arrangements are known. The beamformer characteristics may thereby
be realized by applying a single, discrete input acoustical/electrical converter with
an intrinsic directional characteristic or may be implied by means of more than one
distinct input acoustical/electrical converters, e.g. following the well-known delay-and-add
technique.
[0147] The output signal S
60 in frequency or frequency band domain or a signal dependent therefrom is branched
at branching point P
60. Signal I
62, still dependent on output signal S
60, is input to the input E
62 of a normalizing unit 62. There each frequency sample of prevailing, actual value
is normalized by a signal S
N value fed to normalizing input N
62 of unit 62. For each frequency sample the normalizing unit 62 generates at output
A
62 a normalized value as signal I
62. a signal dependent therefrom being fed to one input E
641 of a comparing unit 64. A storing unit 66 is provided wherein the predetermined roll-off
characteristic RO is stored. The output A
66 thereof is operationally connected to the second input E
642 of comparing unit 64. The output A
64 with the comparison result is fed to a control input C
68 of a selection unit 68. A signal input E
68 of that unit is operationally connected via branching point P
60 to the output A
60 of converter arrangement 60. Unit 68 generates signal S
68 at output A
68.
[0148] The roll-off characteristic RO is defined as the quotient of a spectral component
of a considered frequency at output signal S
60 to the value of the respective component in the acoustical signal impinging on the
sensing area of arrangement 60. From unit 66, for each frequency sample f' a roll-off
value is fed to unit 64. For comparison purposes the respective sample prevailing
in signal I
60 must be normalized before any meaningful comparison may be performed at unit 64 with
the respective frequency-specific roll-off value.
[0149] Thus, the normalizing value S
N fed to normalizing unit 62 must be dependent as accurately as possible on the actual
value of frequency components of the acoustical signal impinging on converter arrangement
60.
[0150] If within the input acoustical/electrical converter arrangement 60 beamforming is
achieved with a single discrete directional converter, as with a microphone with directional
characteristic, preferably a second microphone will be installed e.g. in arrangement
60. Its output signal, after time domain to frequency or frequency band domain conversion,
is operationally connected to the input N
62 of the normalizing unit 62 as normalizing signal S
N. Thereby such an additional acoustical/electrical converter is preferably selected
to have an omnidirectional characteristic.
[0151] As shown in dashed lines in fig. 9 such additional standardizing input converter
70 has an output, in fact forming a further output of converter arrangement 60, which
is operationally connected to the input N
62 of normalizing unit 62 after time to frequency of frequency band domain conversion
TFC at a unit 63. Thus, at the normalizing unit 62 each prevailing frequency sample
of signal I
60 will be normalized with the value of respective spectral component of the acoustical
signal.
[0152] Another possibility of normalizing the signal I
60 in the case of providing a directional input converter in arrangement 60 is to continuously
average the signal after beamforming overall frequencies and over a predetermined
amount of time and to apply the average result to input N
62. In this case the input acoustical/electrical converter arrangement 60 needs only
to be provided with a single input acoustical/electrical converter with intrinsic
beamforming ability and the normalizing signal S
N is established from the signal I
60. Nevertheless it appears that such processing will be less accurate than processing
normalization by the actual spectral component values of the acoustical signal as
is performed with a normalizing omni-directional converter 17.
[0153] Very often the beamforming ability of the input acoustical/electrical converter arrangement
60 is achieved by means of at least two discrete input acoustical/electrical converters,
the output signals thereof being processed e.g. according to the well-known delay-and-add
principal.
[0154] In this case providing normalizing signals is quite simple. This is shown schematically
in fig. 11. The input acoustical/electrical converter arrangement 60a has at least
two distinct input acoustical/electrical converters 70, the output thereof being processed
e.g. and as shown by the well-known delay-and-add method. As each single distinct
converter 70 provides at its output an output signal yet not having been subjected
to beamforming, which is performed in a beamformer processing unit 72, each of the
output signals S
70 and S
70'has spectral components with the value according to that component in the impinging
acoustic signal. The signal of one of the distinct input converters is directly tapped
off after time domain to frequency or frequency band domain conversion to an output
A
60aN of arrangement 60a and a signal dependent therefrom is operationally connected to
the input N
62.
[0155] In comparing unit 64 there is monitored for each frequency sampled whether the actual
normalized value has a predetermined relationship with respect to the roll-off value.
In a most preferred embodiment it is established for each normalized frequency sample
value, whether it is at most equal to the roll-off value. The output signals at the
output A
64 of comparing unit 64 thereby indicate for which specific frequency the normalized
value fulfills the predetermined comparison criterion, thus, as preferred, whether
the normalized value is at most equal to the roll-off value.
[0156] In the selection unit 68, to which by input signal S'
60 the instantaneously prevailing frequency samples are fed, only those samples are
passed for which the normalized samples fulfill the requested predetermined comparison
criterion. Canceling the samples at those frequencies which do not fulfill the comparison
criterion is easily done by establishing in the control signal applied to C
68 a zero for that not fulfilling frequency component and multiplying at the selection
unit 68 the respective frequency samples by zero.
[0157] With an eye on fig. 10 the spectral characteristic (b) represents clean speech, the
characteristics (c) and (d) respectively represent strong and weak wind noise. As
was said characteristic (a) represents typical roll-off characteristic.
[0158] By comparing the characteristics as of fig. 10 with the embodiment and method of
fig. 9, especially with the preferably established comparison criterion according
to which only samples of those frequencies are passed by unit 68, for which the value
of the normalized sample is at most equal to the roll-off value, it may be seen that
all samples Q below the roll-off characteristic (a) will be passed, whereas samples
R above that roll-off characteristic (a) will be cancelled at selection unit 68.
[0159] Following up the description of fig. 9 up to now, the spectral components or frequency
samples prevailing in signal S
62 are rather binaurally passed or not passed to output signal 5
68. Very often and for many appliances as especially for hearing devices, thereby especially
hearing aid devices, such binary switching is not optimal. In fig. 12 there is shown
by means of a simplified schematic signal-flow/functional block representation a preferred
embodiment of establishing control between the comparing unit 64 and frequency sample
selection at a selection unit 68a. The unit 68a as well as 64 are operationally connected
and fed with signals as was described with the help of fig. 9. As was explained with
the help of fig. 9 at the output of comparing unit 64 there appears specifically for
each frequency or frequency band a control signal, which indicates whether the respective
normalized value of the respective samples do or do not fulfill the predetermined
comparison condition. These signals are, according to fig. 12 first operationally
connected to a unit 74 which has a transfer characteristic of low-pass type. This
results in an output signal S
74, which is a continuously varying average signal specifically for each frequency or
frequency band. Thus, the control signals applied to C
68a are not anymore binary pass/not pass control signals for unit 68, but do continuously
or steadily vary between predetermined maximal and minimal values. Additionally the
selection unit 68 of fig. 9 is replaced by a frequency or frequency band selective
attenuation unit 68a, in which frequency or frequency band specifically, the value
of the frequency samples are attenuated, controlled by the frequency- or frequency
band-specific control signals applied to C
68a.
[0160] Thereby, it is achieved that samples at those frequencies, whereat the respective
normalized values do not fulfill the criterion frequently or during predetermined
time spans are more and more attenuated in time up to finally disappearing in output
signal S
68a.
4th aspect
[0161] Under the fourth aspect of the present invention a beamforming technique is proposed
in which frequency or frequency band specifically beamforming may be controlled. This
technique under the fourth aspect of the present invention may be ideally combined
with the technique as was explained in context with fig. 9 to 12, i.e. in context
with the third aspect of the present invention. This invention shall be explained
with the help of fig. 13.
[0162] A beamformer arrangement 80 comprises at least two distinct input acoustical/electrical
converters 80
a and 80
b. The electric outputs of the converters 80
a and 80
b are respectively connected to inputs E
82a and E
82b of respective time domain to frequency or frequency band domain conversion - TFC
- units 82a and 82b.
[0163] The outputs A
82a and A
82b are generically input to a beamformer processing unit shown in fig. 13 within dashed-pointed
lines and referred to by the reference No. 84. When beamformer processing is done
by the known delay-and-add principle, such beamformer processing unit 84 incorporates
a - preferably controlled - delaying unit 86 and an adding/subtracting unit 88. Both
output signals of the TFC units 82a and 82b are operationally connected to the respective
inputs E
84a and E
84b of the beamformer processing unit 84. At least one of the operational connections
between the respective outputs of the TFC units and respective inputs of the beamformer
processing unit 84 comprises a frequency or frequency band selective control unit
90. The control unit 90 has a control input C
90 to which control signals SC
90 are fed.
[0164] The control unit 90 is construed in fact equally to the selection unit 68 of fig.
9 or the attenuation unit 68a of fig. 12.
[0165] To the control input C
90 frequency-specific or frequency band-specific control signals are applied, which
control for each frequency-specific or frequency band-specific samples at the output
of TFC unit 82b, how it is passed to input E
84b of the beamformer processing unit 84. Binary passing/not passing samples of the respective
frequency or frequency band according to the respective frequency- or frequency band-specific
control signal to C
90, means switching the beamforming ability of the beamforming processing unit 84 for
the specific frequencies considered on and off.
[0166] Whenever samples of a specific frequency or frequency band are blocked by control
unit 90 for that specific frequency or frequency band, beamforming ability of processor
unit 84 ceases. There results namely, in that case that such samples of the considered
frequencies or frequency bands are only fed to processor unit 84 from the one remaining
input converter, according to fig. 13 from converter 80a.
[0167] Thereby, here too, it might be advisable not to binarily switch beamforming ability
on and off. Therefore it might be advisable on one hand to provide the control signals
to C
90 via a low-pass type unit 74a, operating as was explained in context with fig. 12
for unit 74 and/or to construe control unit 90 as a frequency- or frequency band-specific
attenuation unit according to unit 68a, which was explained with the help of fig.
12 in context with the third aspect of the present invention.
[0168] Under a generic aspect the frequency- or frequency band-specific control signals
SC
90 of fig. 13 are generated from a control unit 92, which generates at its output Ag
2 frequency- or frequency band-specific control signals for the frequency of frequency
band-specific beamformer ability of acoustical/electrical converter and beamformer
arrangement 80.
[0169] With an eye on noise canceling it is thereby preferred that the addressed control
unit 92 is a frequency- or frequency band-selective noise detector especially a wind
noise detector.
[0170] Switching back to the third aspect of the present invention as disclosed in fig.
9, the normalizing unit 62 and the comparing unit 64, to which the roll-off characteristic
is fed from unit 66 represent in fact a frequency- or frequency band-selective noise
detector unit, thereby even a wind noise detector unit. As has been described, whenever
at unit 64 a predetermined comparison result is achieved, the respective frequency-specific
or frequency band-specific control signal at the output of that unit 64 is indicative
of such a result, and in analogy when the respective comparison result is negative.
Therefore, a control unit 90 as of fig. 13 is preferably construed by a normalizing
unit as of 62, a comparing unit 64 and storing unit 66 as of fig. 9.
[0171] In a most preferred embodiment the invention according to the fourth aspect is combined
with the invention according to the third aspect. In the embodiment of fig. 9, on
one hand, the input converter arrangement 60 is construed as an input converter arrangement
80 of fig. 13. On the other hand, the output of comparing unit 64 is additionally
to be operationally connected to the control input C
68 of selection unit 68, operationally connected to the input C
90 of such input converter arrangement 80.
[0172] By such a combination a most advantageous effect is reached: Whenever samples of
a predetermined frequency or frequency band are more and more attenuated or are blocked
at selection unit 68 or, respectively, at amplification unit 68a as of fig. 12, simultaneously
beamforming ability of the beamforming processing unit 84 with respect to that frequency
or frequency band will be attenuated as well or even completely stopped. By latter
action the roll-of function for that specific frequency or frequency band does not
prevail anymore, because roll-off behavior results from beamforming. Because for the
frequency or frequency band considered, roll-off behavior does not anymore prevail,
there will appear at the output A
80 (Fig. 13) the respective frequency or frequency band component unattenuated by roll-off.
Back to fig. 9, this will lead at comparing unit 64 to the normalized value largely
exceeding the roll-off value at the considered frequency or frequency band, thereby
accelerating the increase of attenuation for such sample at unit 68/68a.
[0173] Thus, combining the teachings of the fourth aspect and of the third aspect of the
present invention leads to improved noise canceling, thereby especially wind noise
canceling at an acoustical device, thereby especially a hearing device and further
preferably a hearing aid device.
Fifth aspect
[0174] Under the fifth aspect of the present invention a wind noise detection technique
is proposed, leading to a method of manufacturing an acoustical device with wind noise
or more generically wind detection ability, further to a respective acoustical device
and to a wind detecting method most preferably applicable for hearing devices, especially
hearing aid devices.
[0175] According to fig. 14 an acoustical/electrical input converter arrangement 100 with
one or more than one distinct acoustical/electrical input converters and having beamforming
ability or not is provided, the output A
100 of which being operationally connected to the input E
102 of a calculating unit 102. In fig. 14 there is schematically shown a spectrum with
amplitude X over frequency axis f. The signal fed to E
102 has a spectrum which accords with or is dependent from the spectrum of acoustical
signals impinging on a sensing area of the arrangement 100.
[0176] Within a predetermined frequency band the spectrum defines for a surface F. The calculation
unit 102 is programmed to calculate from the spectrum at its input E
102 the frequency coordinate f
b of the point of balance P
B of the surface F. This is performed according to the well-known formula as indicated
within the block of calculation unit 102 for calculating the balance point coordinates
of a geometric surface.
[0177] Once within the calculation unit 102 the prevailing frequency coordinate f
b of the balance point P
B is calculated, the respective value forms the basis for deciding by evaluation, whether
wind with a predetermined disturbing effect is present or not. Thereby, evaluation
may comprise checking, whether the frequency coordinate value f
b itself fulfills a predetermined criterion or not. Further and in a preferred embodiment
the average of the frequency coordinate value is calculated continuously over a predetermined
time span, and it is evaluated, whether the average value f
b fulfils a predetermined criterion or not. As a third criterion the variance of the
frequency coordinate f
b is continuously calculated over a predetermined amount of time and again evaluation
is made whether such variance value fulfills a predetermined criterion or not.
[0178] Further, evaluation is preferably done on the basis of the quotient of average value
to variance value of the said frequency coordinate f
b and/or on the basis of the inverse quotient. From combining two or more than two
of these testing criteria there is finally evaluated whether wind and thereby wind
noise is present to a disturbing amount or not. Additional evaluation parameters may
be used and considered in the calculation of calculating unit 102 by respective programming,
so e.g. energy of the signal applied to E
102, SNR with respect to speech signals, etc.
[0179] By the technique according to this fifth aspect of the present invention, wind detection
becomes possible from an acoustical/electrical input converter arrangement, irrespective
of its specific layout. The output of calculating unit 102 is used for appropriately
controlling an acoustical device or for construing an acoustical device which is controlled
according to the prevailing wind characteristics.
[0180] Again and with respect to the methods of manufacturing a device under all aspects
of the invention, the operational connections between the various units are established
preferably at least to a part before assembling the units in respective single or
multiple casings. All aspects of the present invention do not address specific processing
of electric signals representing audio signals according to specific device and/or
individual needs. By the invention according to the present invention it is achieved
- beside of wind recognition per se - that the electric signals at the output of an
input acoustical to electrical converter arrangement representing audio signals are
improved with respect to their relevancy on signals to be tracked as with respect
to signal-to-noise ratio and thereby especially signal-to-wind noise ratio.
[0181] For completeness of disclosure we also refer to the claims as originally filled with
the parent application:
1st aspect
[0182]
- 1. A method for manufacturing an acoustical device, especially a hearing device comprising
the steps of
- providing in a device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing an audio signal processing unit for establishing audio signal processing
of the device according to individual needs and/or purpose of the device, having an
input and an output;
- providing at least one electrical/mechanical output converter with an input;
- providing a filter arrangement with adjustable high-pass characteristic, with a control
input for said characteristic, an input and an output;
- establishing the following operational connections:
between said output of said input converter arrangement and said input of said filter
arrangement,
between said output of said filter arrangement and said control input
between said output of said filter arrangement and said input of said processing unit,
between said output of said processing unit and said input of said at least one output
converter.
- 2. The method of claim 1, further comprising the step of establishing said operational
connection of said output of said filter arrangement and said control input via a
statistic evaluating unit.
- 3. The method of claim 2, further comprising the step of providing said statistic
evaluating unit determining the amount of energy of a signal at said output of said
filter arrangement and further establishing said adjusting for minimizing said energy.
- 4. The method of claim 1, further comprising realizing said filter arrangement with
a predictor unit, preferably by operationally connecting to said output of said input
converter a unit with a predictor unit in the following structure:
- an adjustable low-pass filter with an input operationally connected to said output
of said input converter arrangement and with an output operationally connected to
one input of a comparing unit;
- operationally connecting said output of said input converter arrangement substantially
unfiltered with respect to frequency to a second input of said comparing unit;
- operationally connecting an output of said comparing unit to a control input of said
low-pass filter for adjusting characteristic of said low-pass filter, said control
input of said low-pass filter being said control input of said filter arrangement
and said output of said comparing unit being said output of said filter arrangement.
- 5. The method of one of claims 1 to 4, further comprising providing in said casing
an analog to digital conversion unit and operationally connecting the input of said
analog to digital conversion unit to said output of said input converter arrangement,
operationally connecting the output of said analog to digital converter unit to the
input of said filter arrangement and providing said filter arrangement as a digital
filter arrangement.
- 6. An acoustical device, especially a hearing device, comprising an acoustical/electrical
input converter arrangement;
- a processor unit for establishing signal processing of the device according to individual
needs and/or purpose of the device and having an input and an output;
- at least one output electrical/mechanical converter with an input;
- a filter arrangement with adjustable high-pass characteristic and with an input operationally
connected to an output of said input converter arrangement and further having a control
input for adjusting said characteristic, wherein said control input is operationally
connected to said output of said filter arrangement, said output of said filter arrangement
to said input of said processing unit, the output of which being operationally connected
to said input of said at least one output converter.
- 7. The device of claim 6, wherein said output of said filter arrangement is operationally
connected to said control input via a statistics evaluating unit.
- 8. The device of claim 7, wherein said statistics evaluating unit operates to determine
energy of a signal at said output of said filter arrangement and wherein said high-pass
characteristic is adjusted in dependency of said energy for minimizing said energy.
- 9. The device of claim 6, wherein said filter arrangement comprises a predictor unit
preferably with the following structure:
- an adjustable low-pass filter with said control input and with an input operationally
connected to said output of said input converter and with an output operationally
connected to one input of a comparing unit;
- a second input of said comparing unit being operationally connected to said output
of said input converter without substantial frequency filtering;
- the output of said comparing unit being said output of said filter arrangement.
- 10. The device of one of claims 6 to 9, further comprising an analog to digital converter
unit, an input thereof being operationally connected to the output of said input converter,
the output thereof being operationally connected to said input of said filter arrangement,
said filter arrangement being a digital filter arrangement.
- 11. A method for reducing disturbances, especially wind disturbances, in an acoustical
device, especially a hearing device with an input acoustical/electrical converter
arrangement generating a first electric output signal and comprising the steps of
- filtering a signal dependent from said first electric signal with a variable high-pass
characteristic, thereby generating a second electric signal;
- adjusting said variable characteristic by a third signal dependent on said second
signal.
- 12. The method of claim 11, further comprising the step of generating said third signal
in dependency of said second signal comprising performing a statistical evaluation
on said second signal and generating said third signal in dependency of a result of
said statistical evaluation.
- 13. The method of claim 12, further comprising the step of evaluating by said statistical
evaluation energy of said second signal and adjusting said characteristic in dependency
of said energy so as to minimize said energy.
- 14. The method of claim 11, further comprising the steps of performing said filtering
by predicting a signal dependent from the output signal of said input converter arrangement,
forming a difference from a prediction result and said dependent signal and minimizing
by said filtering and said adjusting said difference.
- 15. The method of claim 11, said step of performing said filtering comprising the
steps of
- low-pass filtering a signal dependent on the output signal of said input converter
arrangement with an adjustable low-pass characteristic;
- comparing an output signal dependent on the result of said low-pass filtering with
a signal dependent from said output signal of said input converter substantially unfiltered
with respect to its frequency content;
- controlling said adjustable high-pass characteristic by controlling said adjustable
low-pass characteristic.
- 16. The method of one of claims 11 to 15, further comprising the step of performing
said filtering and adjusting digitally.
2nd aspect
[0183]
17. A method of manufacturing an acoustical device, especially a hearing device comprising
the steps of
- providing in a hearing device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing a pitch filter with adjustable pitch position, a control input for said
pitch position and with an input and an output;
- providing a pitch detector arrangement with an input and with an output;
- establishing operational connections between:
said electrical output of said input converter arrangement and said input of said
pitch filter;
said output of said input converter arrangment and said input of said pitch detector
arrangement;
said output of said pitch detector arrangement and said control input.
18. The method of claim 17, further comprising providing said pitch detector arrangement
with a further input and establishing operational connection between said output of
said pitch filter and said further input.
19. An acoustical device, especially a hearing device, comprising
- an acoustical/electrical input converter arrangement with an output;
- a pitch filter with adjustable pitch position and a control input for said pitch position,
further with an input and an output;
- a pitch detector unit with an input and with an output, the output of said input converter
arrangement being operationally connected to the input of said pitch filter, the output
of said input converter arrangement being operationally connected to the input of
said pitch detector unit, said output of said pitch detector unit being operationally
connected to said control input.
20. The device of claim 19, said pitch detector unit having a further input operationally
connected to said output of said pitch filter.
21. A method for improving signal-to-noise ratio in an acoustical device, especially
a hearing device comprising pitch filtering a signal dependent from an output signal
of an acoustical/electrical input converter arrangement, monitoring the actual pitch
of predominant frequency components within said dependent signal, adjusting pitch
position of said pitch filtering dependent on said actual pitch position monitored.
22. The method of claims 1 and 17, further comprising the step of establishing said
operational connection of said output of said input converter arrangement and said
input of said pitch filter with adjustable pitch as well as said operational connection
between said output of said input converter arrangement and said pitch detector unit
via said filter arrangement.
23. The device according to claims 6 and 19, said operational connection of said output
of said input converter arrangement to said input of said pitch filter and to said
input of said pitch detector unit comprising said filter arrangement.
24. The method of claims 11 and 21, further comprising the step of performing said
pitch filtering on a signal dependent from said second electric signal.
2nd aspect, 2nd sub-aspect
[0184]
25. A method of manufacturing an acoustical device, especially a hearing device, comprising:
- providing in a hearing device casing an acoustical/electrical input converter arrangement
with an electric output;
- providing an adding unit with at least two inputs;
- providing a first band-pass filter unit with an input and with an output and with
a band selected to pass selected harmonics of speech;
- a non-linear modulation unit with an input and with an output;
- a second band-pass filter unit or a low-pass filter unit, with an input and with an
output and with a pass-band selected to pass selected different harmonics of speech
and establishing the following operational connections:
from the output of said input converter arrangement to one input of said adding unit
without substantial frequency filtering;
from the output of said input converter arrangement to the input of said first band-pass
filter unit, without substantial frequency filtering;
from said output of said first band-pass filter unit to the input of said non-linear
modulation unit;
from the output of said non-linear modulation unit to the input of said second band-pass
filter or low-pass filter unit,
from said output of said second band-pass filter or said low-pass filter unit to the
second input of said adding unit.
26. The method of claim 25, further comprising providing an analog to digital conversion
unit with an input and with an output and establishing said operational connection
between said output of said input converter arrangement and said one input of said
adding unit as well as to said input of said first band-pass filter unit via said
analog to digital conversion unit and providing said filter units, said non-linear
modulation unit and said adding unit as digital units.
27. An acoustical device, especially a hearing device comprising an acoustical/electrical
input converter arrangement with an output, a first band-pass filter unit with an
input and with an output, and with a band selected to pass selected harmonics of speech,
a non-linear modulation unit with an input and with an output, a second band-pass
filter or low-pass filter unit selected to pass different selected harmonics of speech,
with an input and with an output, an adding unit with two inputs and with an output,
wherein said output of said input converter arrangement is operationally connected
to a first input of said adding unit substantially without frequency filtering, said
output of said input converter arrangement is operationally connected to the input
of said first band-pass filter unit, the output of which being operationally connected
to the input of said non-linear modulation unit, the output of which being operationally
connected to said input of said second band-pass filter or of said low-pass filter
unit, the output thereof being operationally connected to the second input of said
adding unit.
28. The device of claim 27, further comprising an analog to digital converter unit
interconnected between said output of said input converter arrangement and said one
input of said adding unit as well as said input of said first band-pass filter unit,
said filter units, said non-linear modulation unit and said adding unit being digital
units.
29. A method for increasing signal-to-noise ratio at an acoustical device, especially
a hearing device and with respect to speech signal with an acoustical/electrical input
converter arrangement generating a first electric signal, comprising the steps of
- band-pass filtering a signal dependent on said first signal to generate a band-pass
filtered signal with harmonic components of speech;
- modulating said filtered signal at a non-linear characteristic to generate an output
signal with a re-increased number of harmonic components of speech;
- band- or low-pass filtering said output signal with said increased number of harmonic
components, to generate a further signal with selected harmonic components and superposing
said further signal to a signal dependent on said first electric signal.
30. The method of claims 1 and 25, further comprising the step of establishing operational
connection of said output of said input converter arrangement and said one input of
said adding unit as well as to said input of said first band-pass unit via said filter
arrangement.
31. The device of claims 6 and 27, further comprising operationally connecting said
output of said input converter arrangement to said one input of said adding unit as
well as to said input of said first band-pass unit via said filter arrangement.
32. The method of claims 11 and 29, wherein said step of generating said signal dependent
on said first signal comprises filtering said first electric signal with said variable
high-pass characteristic.
3rd aspect
[0185]
33. A method of manufacturing an acoustical device, especially a hearing device, comprising
the steps of
- providing in a device casing an acoustical/electrical input converter arrangement,
generating at an output an electrical signal in frequency or frequency band domain
with a beamformer amplification characteristic of acoustical signals impinging on
said arrangement in dependency of impinging angle with which said acoustical signals
impinge thereon and with a predetermined frequency roll-off characteristic of said
beamformer characteristic;
- providing a normalizing unit with an input and with an output and establishing operational
connection of said output of said arrangement and said input of said normalizing unit;
- providing a memory unit with said predetermined roll-off characteristic stored therein;
- providing a comparing unit;
- establishing operational connection between the output of said normalizing unit and
one input of said comparing unit as well as between said output of said storing unit
and a second input of said comparing unit;
- providing a controlled selection unit with a control input, an input and an output
and establishing an operational connection between said output of said arrangement
and said input of said selection unit as well as between said output of said comparing
unit and said control input of said selection unit, said selection unit being controlled
to alternate frequency components of said electric signal to its output, the normalized
values of which non resulting in a predetermined comparison result at said comparing
unit.
34. The method of claim 33, further comprising the step of providing said input converter
arrangement with at least two input acoustical/electrical converters.
35. The method of claim 34, further comprising providing at least two time domain
to frequency or frequency band domain conversion units - TFC - each with an input
and an output and establishing an operational connection of a first of said at least
two input converters with the input of a first of said at least two TFC converter
units and of a second of said at least two input converters with the input of a second
of said at least two TFC converter units.
36. The method of claim 34, further comprising the step of providing said beamformer
characteristic by providing a beamformer unit with at least two inputs and establishing
a first operational connection between an output of a first of said at least two input
converters and a first of said at least two inputs of said beamformer unit and a second
operational connection between an output of a second of said at least two input converters
and a second of said at least two inputs of said beamformer unit.
37. The method of claim 36, further comprising providing at least two time domain
to frequency or frequency band domain conversion - TFC - units and establishing said
first and second operational connections each via one of said at least two TFC units.
38. The method of claim 37, further providing said beamformer unit with a control
input and establishing an operational connection between the output of said comparing
unit and said control input of said beamformer unit.
39. The method of claim 34, further comprising the step of providing said input converter
arrangement with a further output and establishing an operational connection between
an output of one of said at least two input converters and said further output and
between said further output and a further input of said normalising unit for a normalising
signal.
40. The method of claim 39, further providing said input converter arrangement with
said further output providing a output signal in frequency or frequency band domain.
41. The method of claim 33, further providing a signal transfer unit with a low-pass
type signal transfer between an input and an output and operationally interconnecting
said signal transfer unit between said output of said comparing unit and said control
input of said selection unit.
42. The method of claim 33, further comprising the step of establishing said predetermined
result as said normalized values being at most equal to said predetermined roll-off
characteristic values at the frequencies considered.
43. An acoustical device especially a hearing device comprising
- an input acoustical/electrical converter arrangement having an output and generating
an output signal at said output with a beamformer amplification characteristic dependent
on the direction with which acoustical signals impinge upon said arrangement and having
a predetermined frequency roll-off characteristic of said beamformer characteristic
and further being in the frequency or frequency band domain,
- a normalizing unit, an input of which being operationally connected to the output
of said arrangement, an output of which being operationally connected to one input
of a comparing unit;
- a memory unit with said predetermined roll-off characteristic stored therein, an output
of which being operationally connected to a second input of said comparing unit;
- a controlled selection unit with a control input and an input operationally connected
to the output of said arrangement, said control input of said selection unit being
operationally connected to said output of said comparing unit, said selection unit
controllably attenuating frequency components in a signal input to a signal output
for which comparison has not resulted in a predetermined result, differently than
such components for which said comparison has resulted in said predetermined result.
44. The device of claim 43, said input converter arrangement comprising at least two
input acoustical/ electrical converters, each with an output.
45. The device of claim 44, further comprising at least two time domain to frequency
or frequency band domain conversion units TFC, each with an input and with an output,
the output of a frist of said at least two input converters being operationally connected
to the input of a first of said TFC units, the output of a second of said input converters
being operationally connected to the input of a second of said TFC units.
46. The device of claim 44 further comprising a beamformer unit with at least two
inputs, one input thereof being operationally connected to an output of one of said
at least two input converters the other input thereof being operationally connected
to an output of a second of said at least two input converters.
47. The device of claim 46, comprising at least two TFC units, one operationally interconnected
between said one input of said beamformer unit and said output of said first input
converter the second operationally interconnected between said input of said second
TFC unit and said output of said second input converter.
48. The device of claim 47, said beamformer unit comprising a control input being
operationally connected to the output of said comparing unit.
49. The device of claim 43, wherein said comparison results act upon said attenuating
with a low-pass-type transfer function.
50. The device of claim 44, said arrangement comprising a further output operationally
connected to an output of one of said at least two input converters, said output being
operationally connected to a further input of said normalizing unit for a normalizing
signal.
51. The device of claim 43, wherein said predetermined result is that said normalized
value is at most equal to said predetermined roll-off characteristic value.
52. A method for at least substantially canceling wind disturbances in a acoustical
device especially in a hearing device with an input acoustical/electrical converter
arrangement, said arrangement generating at an output an electric signal in frequency
or frequency band domain with a beamformer amplification characteristic with respect
to the impinging angle with which acoustical signals impinge upon said arrangement
and with a predetermined frequency roll-off characteristic comprising the steps of
normalizing a signal dependent on said electric signal in frequency domain, comparing
frequency- or frequency band-specifically said normalized signals with said respective
values of said frequency roll-off characteristic and attenuating frequency signal
components of said electric signal in dependency of results of said comparing.
53. The method of claim 52, comprising the step of frequency selectively normalising
said signal dependent on said electric signal by signal values which depend from values
of respective frequency components of said impinging acoustical signal by a predetermined,
frequency independent factor.
54. The method of claim 52, further comprising the step of generating said beamformer
characteristic by at least two input acoustical/electrical converters in said input
converter arrangement.
55. The method of claim 53, further comprising the step of generating said values
by an input acoustical/electrical converter at said input converter arrangement.
56. The method of claim 52, further comprising establishing dependency of said attenuating
from said results with a low-pass type dependency.
57. The method of claim 52, thereby selecting said comparing as determining whether
said normalised signals are or are not at least equal to respective values of said
predetermined roll-off characteristic and selecting said attenuation to be the larger
for signals for which comparison result is of affirmative or negative.
58. The method of claim 52, further comprising frequency selectively attenuating beamforming
in dependency of said results.
59. The method of claim 58, further comprising establishing said dependency with a
low-pass-type characteristic.
4th aspect
[0186]
60. The method of manufacturing a beamforming device comprising:
- providing in a casing of said device a beamformer unit operating in frequency or frequency
band domain
- providing at said beamformer unit a control input frequency or frequency band selectively
controlling beamforming of said beamformer unit
- providing a control unit having an output for frequency or frequency band selective
control signals and
establishing an operational connection between the output of said control unit and
said control input.
61. The method of claim 60, further comprising the step of providing said control
unit with a frequency or frequency band selective noise detector.
62. The method of claim 60, further comprising the step of providing said control
unit with a wind-noise detector and said beamformer unit with an acoustical/electrical
converter arrangement.
63. The method of claim 60, further comprising the step of providing said beamformer
unit with at least two
- input converters each having an output;
- providing at least one controlled frequency of frequency band selective attenuation
unit with a frequency or frequency band selective attenuation control input, an input
and an output
- providing a beamformer processing unit with at least two inputs and an output
- establishing operational connections between:
- an output of one input converter via said attenuation unit to one input of said processing
unit
- an output of a second input converter to a second input of said processing unit
said output of said control unit and said control input of said attenuation unit.
64. The method of claim 60, said beamforming device being an acoustical device, especially
a hearing device.
65. A beamforming device comprising
a beamformer unit operating in frequency or frequency band domain and having a control
input for frequency or frequency band selectively controlling beamforming
a control unit having an output for frequency or frequency band selective control
signals being operationally connected to said control input.
66. The device of claim 65 said controlling unit comprising a frequency or frequency
band selective noise detector.
67. The device of claim 65, said controlling unit comprising a wind noise detector
and said device being an acoustical/electrical beamforming device.
68. The device of claim 65, said beamformer unit comprising at least two input converters
each with an output and a beamformer processing unit with at least two inputs and
an output
- at least one controlled frequency or frequency band selective attenuation unit with
a frequency or frequency band selective attenuation control input and an output
said output of one of said input converters being operationally connected to one input
of said processing unit via said attenuation unit,
said output of a second of said input converters being operationally connected to
a second input of said processing unit, said output of said control unit being operationally
connected to said control input of said alternation unit.
69. The device of claim 65 being an acoustical device, especially a hearing device.
70. The method for controlling beamforming comprising the steps of performing beamforming
in frequency or frequency band domain, controlling beamforming frequency or frequency
band selectively.
71. The method of claim 70, further comprising the step of controlling beamforming
in dependency of frequency or frequency band specific disturbances.
72. The method of claim 70, said beamforming being an acoustical/electrical beamforming
and controlling said beamforming in dependency of prevailing wind noise.
73. The method of claim 70 for controlling acoustical/electrical beamforming especially
of a hearing device.
74. The method of claim 70, comprising the step of performing said beamforming by
processing output signals of at least two input converters in frequency or frequency
band domain and applying a controllable, frequency or frequency band specific attenuation
to at least one of said output signals in said domain.
5th aspect
[0187]
75. A method of manufacturing an acoustical device comprising
- providing a acoustical/electrical input converter arrangement into a casing of the
device said arrangement having an output
- providing a calculation unit with an input and an output
establishing an operational connection between said output of said converter arrangement
and said input of said calculation unit programming said calculation unit to calculate
from a signal input the frequency-coordinate value of the balance point of a surface
of the spectrum in a predetermined frequency range and generating an output signal
in dependency of said coordinate value indicative of wind noise.
76. The method of claim 75, further comprising programming said unit to continuously
average said coordinate value over a predetermined amount of time and/or to continuously
calculate the variance of said coordinate value over a predetermined amount of time,
generating said output signal comprising generating said output signal at least in
dependency of said average and/or said variance.
77. The method of claim 75, said device being a hearing device.
78. An acoustical device comprising an acoustical/electrical input converter arrangement
with an output, a calculation unit with an input operationally connected to said output
and being programmed to calculate from a input signal at said input the frequency-coordinate
value of the balance point of a surface of the spectrum in a predetermined frequency
range and to generate an output signal in dependency of said coordinate value indicative
of wind noise.
79. The device of claim 75, said calculation unit being further programmed to continuously
calculate average value of said coordinate value over a predetermined amount of time
and/or the variance of said coordinate value over a predetermined amount of time,
generating said output signal comprising generating said output signal in dependency
of at least at least one of said average and said variance.
80. The device of claim 78 being a hearing device.
81. A method of detecting wind noise at an acoustical device with acoustical/electrical
conversion to generate an electric signal comprising the steps of electronically calculating
the frequency coordinate value of the balance point of the spectrum of said signal
within a predetermined frequency range and generating a wind noise indicative signal
in dependency of said value.
82. The method of claim 81, further comprising continuously calculating an average
value over a predetermined amount of time of said coordinate value and/or variance
of said coordinate value over a predetermined amount of time and generating said wind
noise indicative signal in dependency at least of at least one of said average value
and of said variance.
83. The method of claim 81 said device being a hearing device.