FIELD OF THE INVENTION
[0001] The invention relates to a surface mountable microphone comprising:
a case to protect the microphone;
an acoustic sensor to transform sound waves into an electrical microphone signal;
an electrical connector to provide the microphone signal.
BACKGROUND OF THE INVENTION
[0002] Prior art systems comprise a large number of sensors like microphones or vibration
sensors mounted in different locations of an area or surface to measure analogue sensor
signals, which signals are analyzed in an analyzer to which all sensors are connected.
As a result, the analyzer provides information about physical parameters like sound
or vibration in this area where the sensors are located. One practical example is
to attach a high number of surface mountable microphones to the surface of a wing
of a test airplane to locate turbulences of the airstream in a wind channel by the
noise generated by a turbulence.
[0003] Document
EP 1 694 718 B1 describes a surface mountable electret condenser microphone, which may be attached
to a surface by e.g. glue as a fastener. Such known surface mountable microphones
are problematic to be used for tests like the one explained above, as after the location
of a turbulence on the wing is identified all the microphones need to be dismounted
to rework the surface of the wing. The destructive removal of the microphones and
the glue leads to mechanical effects on the wing what is problematic.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to provide a surface mountable microphone that may
be used for consecutive tests without the risk of influences to the test result. This
object is achieved with a surface mountable microphone that comprises mounting means
that enable a non-destructive dismounting and remounting of the microphone to a surface.
[0005] A microphone according to the invention comprises the advantage that the microphones
may be dismounted after each test and mounted again onto the surface to be tested,
without the risk of influencing the comparability of consecutive tests. A simple way
to realize such mounting means would be one or more magnets within or as part of the
case of the microphone which magnets generate magnetic forces towards a metallic surface
to be tested. This simple realization works only in systems where the surface to be
tested interacts with the magnets of the mounting means to generate a force that fixes
the microphone to the surface.
[0006] It provides advantages to split the mounting means of the microphone into two separate
elements, case mounting means and surface mounting means. According to one embodiment
of the invention, case mounting means are realized by one or more magnets within the
case of the microphone. For this embodiment, surface mounting means are realized by
e.g. a flat metal ring glued to the surface to be tested. After each test, the microphones
may be detached from the surface in a non-destructive way against the magnetic forces
of the magnets, while only the metal rings stay glued on the surface. After the surface
has been reworked based on the test result, the microphones are again positioned onto
the metal rings which ensures a more or less exact positioning of all microphones
to the same positions as they have been positioned during the preceding test. It is
in particular advantageous to add positioning means to the case mounting means and
surface mounting means to ensure exact positioning with an accuracy of only splits
of a millimeter to ensure comparable consecutive test results.
[0007] These and other aspects of the invention will be apparent from and elucidated with
reference to the embodiments described hereinafter. The person skilled in the art
will understand that various embodiments may be combined.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
Figure 1 shows a top view of part of a wing of an airplane with an array of surface
mountable microphones.
Figure 2 shows a diagonal view of a surface mountable microphone with mounting means.
DETAILED DESCRIPTION OF EMBODIMENTS
[0009] Figure 1 shows a top view of part of a wing 1 of an airplane with an array 2 of surface
mountable microphones 3 attached to the wing 1. Each of these microphones 3 is connected
by a coax-cable 4 to a signal analyzer 5. During a test flight or within a wind tunnel,
wing 1 is exposed to a laminar air stream 6 that may cause turbulences in an area
7 and vibrations in an area 8. As a result of this test, wing 1 needs to be reworked
to improve the aerodynamics, for which work microphones 3 need to be detached first.
After the rework has been finished, microphones 3 need to be attached again for the
next test to check the improvement. It is essential to attach each of the microphones
3 to exact the same position on wing 1 where it was attached during the first test
to ensure comparability of the tests to detect whether or not the rework helped to
reduce turbulences and vibrations on wing 1.
[0010] Figure 2 shows a diagonal view of one of the surface mountable microphones 3 of figure
1. Microphone 3 comprises a case 9 with a microphone case part 10 that protects an
acoustic sensor of microphone 3. The acoustic sensor is realized with a diaphragm
exposed to the air surrounding microphone 3, which diaphragm moves with pressure changes
in the air, which cause changes in an electric microphone signal by changing capacities.
These kind of acoustic sensors, known as electret condenser microphones, are well
known to a man skilled in the art and disclosed e.g. in
EP 1 69 718 B1.
[0011] Microphone 3 furthermore comprises an electrical connector 11 to connect the coax-cable
4 to deliver the microphone signal to analyzer 5. In another embodiment of the invention
other kind of cables with three or more electrical connections and other kind of electrical
connectors could be used as well.
[0012] Microphone 3 furthermore comprises mounting means 12 that enable a non-destructive
dismounting and mounting to the surface of wing 1 or other surfaces to be tested.
Mounting means 12 are realized by case mounting means 13 that are connected by a screw
14 to microphone case part 10 and together form case 9 of microphone 3. Case mounting
means 13 are realized with a hollow body that forms a back volume for the acoustic
sensor what improves the quality of the microphone sensor signal. Case mounting means
13 comprise magnets 15 arranged within the hollow body.
[0013] Mounting means 12 furthermore comprise surface mounting means arranged outside of
case 9 and separated from case 9 and realized by a metal ring 16 glued to the surface
of wing 1. Magnets 15 of case mounting means 13 generate an attraction force 17 towards
metal ring 16 to non-destructive connect case 9 of microphone 3 with metal ring 16
fastened to wing 1 in a way that only enables the glue destroying dismounting of metal
ring 16 from wing 1. This concept of separated surface and case mounting means ensures
easy and non-destroying dismounting and mounting as often as needed while the exact
position is kept by surface mounting means to ensure that microphones 3 of array 2
are arranged with the same geometrical distances for all tests to be made.
[0014] Mounting means 12 furthermore comprise positioning means to position case mounting
means 13 to metal ring 16 in a predefined position. These positioning means are realized
by truncated cone areas 18 of case mounting means 13 and metal ring 16. This provides
the advantage that each of the microphones 3 is positioned very exact and accurate
to always the same position on the surface to be tested each time they are mounted
on metal ring 16 again. Although microphone 3 is positioned by truncated cone areas
18, it still may be rotated, what helps to ensure an easy connection with coax-cables
4. In another embodiment of the invention, positioning means are realized to position
the microphone not only to a concrete exact position on the surface, but in addition
positon the microphone in a defined orientation. In a simple way this might be realized
by a pin and a hole in the case mounting means or the surface mounting means. This
may be advantageous in case the acoustic sensor of the microphone has a direction
dependent sensitivity.
[0015] Electrical connector 11 is arranged on case 9 and in particular in the sidewall of
case mounting means 13. Therefore, an area 19 of case mounting means 13 that mechanically
connects to an area 20 of metal ring 16 is free of any electrical connections to enable
electrically passive surface mounting means. This ensures mechanically simple and
easy to manufacture metal rings 16 of which a high number of pieces have to be glued
test wing 1 and might not be removed anymore even after the tests.
[0016] Microphone 3 furthermore comprises a transparent plastic ring 21 with at least one
LED connected to electrical connector 11 to realize optical signaling means to visualize
the status or other information of microphone 3. This has the advantage that e.g.
analyzer 5 may switch LEDs of microphones 3 in a blinking mode, if a remote test of
the correct functionality of all microphones 3 of array 2 revealed that some of the
microphones 3 are defect and need to be replaced.
[0017] In a further embodiment of the invention, case mounting means and surface mounting
means are built to use adhesive forces of the surfaces they are connected with to
hold the case mounting means and the surface mounting means together. A user may easily
detach or dismount and again attach or mount the microphone in a non-destructive way.
In a further embodiment, electrostatic forces may be generated via coax-cable 4 to
hold case mounting means and the surface mounting means together.
[0018] In another embodiment of the invention, other types of acoustic sensors known to
a man skilled in the art could be used as well. The same advantages as described above
would be achieved for such surface mountable microphones.
1. A surface mountable microphone (3) comprising:
a case (9) to protect the microphone (3);
an acoustic sensor to transform sound waves into an electrical microphone signal;
an electrical connector (11) to provide the microphone signal, characterized in, that the microphone (3) comprises mounting means (12) that enable a non-destructive dismounting
and remounting of the microphone (3) to a surface.
2. Microphone (3) according to claim 1, wherein the mounting means (12) comprise:
case mounting means (13) realized by or within the case (9);
surface mounting means (16) arranged outside of the case (9) and separated from the
case (9); wherein the case mounting means (13) and/or the surface mounting means (16)
are built to generate magnetic and/or electrostatic and/or adhesive attraction forces
for non-destructive dismounting and remounting of the case mounting means (13) to
the surface mounting means (16) and wherein the surface mounting means (16) comprise
a fastener to mount the surface mounting means (16) to the surface in a way that only
enables destructive dismounting.
3. Microphone (3) according to claim 2, wherein the case mounting means (13) comprise
at least one magnet (15) and wherein the surface mounting means (16) are built with
metallic material that generates attraction forces (17) with the at least one magnet
(15).
4. Microphone (3) according to any of the claims 2 to 3, wherein the mounting means (12)
comprise positioning means to position the case mounting means (13) to the surface
mounting means (16) in a predefined positon.
5. Microphone (3) according to claim 4, wherein the positioning means are realized by
truncated cone areas (18) of the case mounting means (13) and the surface mounting
means (16).
6. Microphone (3) according to any of the claims 2 to 5, wherein the case (9) comprises:
a microphone case part (10) that protects the microphone (3) and is connected to case
mounting means (13), which forms a back volume for the microphone (3).
7. Microphone (3) according to any of the claims 2 to 6, wherein the electrical connector
(11) is arranged on the case (9) separated from an area (19) of the case mounting
means (13) that mechanically connects to an area (20) of surface mounting means (16)
to enable electrically passive surface mounting means (16).
8. Microphone (3) according to any of the claims 1 to 7, wherein the case (9) comprises
optical signaling means (21) to visualize information of the microphone (3).