EP3599769A1

EP3599769A1 - Replacable measurement microphone

Info

Publication number: EP3599769A1
Application number: EP18185949.7A
Authority: EP
Inventors: Jonas Bovin; Rene Jensen; Gert Plenge
Original assignee: GRAS Sound & Vibration AS
Current assignee: GRAS Sound & Vibration AS
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-01-29

Abstract

A surface mountable microphone (3) which comprises a case (9) to protect the microphone (3) and an acoustic sensor to transform sound waves into an electrical microphone signal and an electrical connector (11) to provide the microphone signal furthermore comprises mounting means (12) that enable a nondestructive dismounting and remounting of the microphone (3) to a surface.

Description

FIELD OF THE INVENTION

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

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.
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

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.
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.
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.
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

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

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.
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 .
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.
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.
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.
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.
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.
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.
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.
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.

Claims

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.
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.
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).
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.
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).
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).
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).
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).