[0001] The present invention relates to a sound signal processing method of the kind set
forth in the preamble of claim 1 and a device for implementing such a method.
[0002] In signal processing methods of this kind, which are primarily intended for use in
hearing aids of different kinds, it is known from e.g. EP-064,042 to provide a signal
processor which is controlled by several control parameters supplied from a programmable
controller. In the above document, the programmable controller is able to discriminate
between a limited number of discrete acoustical environments and set the control parameters
to provide a limited number of preprogrammed transfer functions for the signal processor,
the transfer functions being selected to best suit the particular acoustical environment.
The changing of control parameters may be performed manually or automatically, the
automatic changing being dependent on the acoustical environment as detected in the
signal processing unit.
[0003] It is the object of the present invention to provide a signal processing method of
the kind mentioned above, with which it is possible to achieve a continuum of dynamically
generated control parameters for the signal processing, whereby an almost unlimited
number of different signal processings of the input signal can be performed, primarily
dependent on the input signal.
[0004] This is achieved with a signal processing method of said kind, which in accordance
with the present invention comprises the features set forth in the characterizing
clause of claim 1.
[0005] With this method it is possible to change the processing parameters for the signal
processing unit dynamically and continuously in accordance with the instantaneous
input signal, so that the processing at all times can be optimized to provide the
desired output signal.
[0006] In a preferred embodiment, further parameters may be used to influence the generating
of the control parameters and accordingly the processing. These parameters may comprise,
but are not limited to, the output signal from the signal processor unit, time of
day, ambient temperature, ambient air humidity, ambient light, telecoil detection,
voice recognized spoken control words, pulse rate of the user, etc., all of these
parameters being supplied to the programmable controller in order to detect different
conditions with respect to e.g. the environment, the "state" of the user, etc.
[0007] The different parameters may initially influence the generated control parameters
according to a preprogrammed function in the programmable controller, but will during
a training period be changed and adjusted in accordance with the preferences of the
user, as communicated to the programmable controller, thereby providing a trainable
performance of the signal processing, in which the starting point is fixed, but the
adjustments are unknown and the final programming is unlimited.
[0008] The signal processing method is preferably implemented in micro-processor technology
and comprises fixed and adjustable programming, the adjustments of the adjustable
programming being normally performed by the user possibly in cooperation with a fitter.
The digital signal processor unit may be implemented in micro-processor technology
as a fixed calculating structure, e.g. a FIR-filter, an IIR-filter, a neural network
or the like, with variable parameters controlled by the programmable controller which
is preferably implemented in the same micro-processor as the signal processing unit.
The programmable controller may perform functions like spectral analysis, statistical
analysis, mathematical functions, logical functions, etc., in order to generate appropriate
control parameters for the digital signal processor unit.
[0009] In the following detailed part of the present description, the invention will be
explained in more detail with reference to the exemplary embodiment of a method of
signal processing and a device for implementing the method according to the invention,
as illustrated schematically in the drawings, in which
Figure 1 shows the main blocks of a hearing aid implementing the method in accordance
with the invention,
Figure 2 shows a more detailed schematic block diagram of an example of signal processing
using a programmable controller with pre-processing, neural network and post-processing
to generate the parameters for a signal processing unit comprising separate filter
and gain blocks, and
Figure 3 shows the performance of the signal processing system in Figure 2 as a function
of the control parameters generated in the pre-processing.
[0010] The hearing aid shown in Figure 1 includes a main signal path comprising a microphone
1, an A/D-converter 2, a digital signal processor unit 3, a D/A-converter 4 and a
telephone 5. The processing in the digital signal processor 3 is controlled by several
control parameters supplied from a programmable controller 6. The programmable controller
6 generates the control parameters continuously and dynamically as a function of the
digitized version of the signal to be processed, delivered by the A/D-converter 2.
In the hearing aid shown in Figure 1, the programmable controller 6 is also receiving
the digital output signal from the digital signal processor unit 3 for influencing
the generating of control parameters for the digital signal processor 3. Further parameters,
as mentioned above, may be supplied to the programmable controller 6 for influencing
the generating of control parameters. The digital signal processor unit 3 is understood
to be a fixed calculating structure, e.g. a FIR-filter, an IIR-filter, a neural network
or the like. It is essential when choosing this fixed calculating structure with adjustable
parameters that the structure can change in characteristics by adjusting the parameters
so that the desired signal processing can be achieved.
[0011] By the shown structure the following advantages are achieved:
[0012] The main signal path is of a constant nature comprising A/D-, D/A-converter and the
digital signal processing unit 3 which once and for all can be constructed to have
sufficient accuracy and resolution to achieve the desired high signal quality.
[0013] New forms of signal processing will only indirectly influence the signal path by
being implemented in the programmable controller 6 which means that the system will
not have to be redesigned with respect to signal/noise-ratio etc., for each new algorithm
to be added.
[0014] With this new concept of a hearing aid, it will be necessary to revise the traditional
concept of serial/parallel manipulation of the signal which cannot be converted sensibly
in this new concept. Accordingly, the opinion of the concept of a hearing aid and
what it can do will have to be revised.
[0015] The adjustment of the hearing aid will possibly comprise a basic adjustment of the
hearing aid in order to compensate for the hearing loss of the patient, which adjustment
will be based on traditional audiologic diagnostics and/or other, possibly individual
characteristics like lifestyle, personal qualities, etc., and followed by further
adjustments of the system in the user's own environment in accordance with the user's
preferences. The aim of these adjustments will be to provide the user with a sound
perception in accordance with the users preferences under different conditions. The
system for fitting the hearing aid will comprise the physical hearing aid and possibly
stationary equipment at the fitter laboratory and user portable equipment for use
in the user's own environment. The communication between the user and the fitting
equipment may be performed by voice control, manual keyboard control, physiologic
activity control, using electrodes or other sensors connected to the user, etc., and
the communication between the fitting equipment and the hearing aid may be wired or
wireless.
Example of signal processing implemented in a system as described above:
[0016] To illustrate the invention, an example is given of a system implementing signal
processing as described above. Figure 2 schematically shows the signal processing
system. Within the system, the programmable controller 6 is built up of three components,
a pre-processing block 7,8, a neural network block 9 and a post-processing block 10.
The signal processing unit 3 is composed of a filter block 11 succeeded by a gain
block 12, both getting parameters from the post-processing block 10. Within the pre-processing
block 7,8 the overall rms-energy (RMS
Total) 8 of the input signal and the ratio between energy at high and low frequencies (Tilt)
7 in the input signal are estimated. According to the instantaneous input signal the
control parameters RMS
Total and Tilt change the processing parameters for the signal processing unit 3, i.e.
the filter coefficients and the gain scaling, dynamically and continuously. The individual
adjustment of the system performance to fulfil the user's preference is carried out
by training the neural network 9 to match the individual requests according to the
control parameters. The achieved functionality is schematically shown in Figure 3.
1. Method of sound signal processing in a signal processing device including a main signal
path comprising
- input means,
- a signal processor unit, and
- output means,
the signal processor being controllable via several control parameters supplied from
a programmable controller, characterized by
generating the control parameters continuously and dynamically in the programmable
controller as a function of at least the sound environment.
2. Method in accordance with claim 1, characterized by further parameters being supplied to the programmable controller for influencing
the generating of control parameters for the signal processor.
3. Method in accordance with claim 2,
characterized by the further parameters comprising:
- the signal to be processed and/or
- the output signal from the signal processor unit and/or
- time of day and/or
- ambient temperature and/or
- ambient air humidity and/or
- ambient light and/or
- telecoil detection and/or
- voice recognized spoken control words etc.
4. Method in accordance with any of the preceding claims, characterized by the programmable controller comprising fixed programming and adjustable programming.
5. Method in accordance with any of the preceding claims, characterized by the signal processor unit implementing a fixed calculating structure, e.g. a FIR-filter
and/or an IIR-filter and/or a neural network, with variable parameters controlled
by the programmable controller.
6. Method in accordance with any of the preceding claims, characterized by the programmable controller being programmed to perform spectral analysis and/or
statistical analysis and/or mathematical and logical functions, in order to generate
the control parameters for the signal processor.
7. Method in accordance with any of the preceding claims, characterized by the programmable controller and/or the signal processor being preceded by a pre-processing
and/or succeeded by a post-processing.
8. Device for implementing the method in accordance with any of the claims 1-7, characterized by the signal processor (3) being implemented in microprocessor technology as a digital
signal processor and the programmable controller (6) being implemented in microprocessor
technology, possibly in the same microprocessor as the digital signal processor (3).
9. Device in accordance with claim 8,
characterized by being implemented in any of the following:
a) a hearing aid
b) a mobile telephone
c) a sound reproduction system
d) a head set
e) a hearing protection device
f) a cochlear implant, etc.
10. Method for adjusting a device in accordance with claim 8 or 9 comprising
a) basic adjustment of the transfer function in accordance with audiologic diagnostics
and/or other individual characteristics like lifestyle, personal qualities, etc.,
to compensate for the hearing loss of the patient,
characterized by further comprising:
b) further adjustment of the programmable controller (6) to influence the parameters
for the digital signal processor (3) in order to make the transfer function dependent
on the acoustical environment and possible further parameters influencing the patient's
perception of the sound, to achieve a final adjustment as close as possible to the
requirements of the individual user under different situations.
11. Method in accordance with claim 10, characterized by further adjustments being performed by the user, possibly in co-operation with
the fitter.
12. Method in accordance with any of the claims 10 or 11, characterized by comprising the use of stationary adjustment equipment and/or user portable adjustment
equipment communicating wired or wireless with the device.
13. Method in accordance with claim 12,
characterized by the stationary adjustment equipment and/or the user portable adjustment equipment
being controlled by any of the following:
a) voice control
b) manual keyboard control
c) physiologic activity control, using electrodes or other sensors connected to the
user.