Microphone and a method of manufacturing a microphone

• US 20060284516A1
• Filed: 06/08/2006
• Published: 12/21/2006
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation), University of Tokyo
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation), University of Tokyo
• Inventors: Mitsushima, Yasuichi, Funabashi, Hirofumi, Nakagawa, Toshiaki, Shimaoka, Keiichi, Ando, Shigeru, Ono, Nobutaka, Wakita, Toshihiro
• Granted Patent: US 7,888,840 B2
• Time in Patent Office: Days
• US Class Current: 310/322
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A microphone that may identify the direction along which acoustic waves propagate with one diaphragm, and which has superior durability is provided. The microphone comprises a circular diaphragm. The diaphragm is supported at the center portion thereof. When the diaphragm receives acoustic waves, each position around the center thereof will vibrate with a phase depending upon the direction of the acoustic waves. First electrodes are arranged on one of the surfaces of the diaphragm. Second electrodes are arranged so that each second electrode faces corresponding first electrode with gap. Each first electrode and corresponding second electrode facing thereto form a first capacitor. Third electrodes are arranged on the other surface of the diaphragm. Fourth electrodes are arranged so that each fourth electrode faces corresponding third electrode with gap. Each third electrode and corresponding fourth electrode facing thereto form a second capacitor. The controller applies a voltage to each of the second capacitors so that the capacitance of each of the first capacitors will be a constant value. The controller identifies the direction along which the acoustic waves propagate based on the difference in the voltages applied to each of the second capacitors. Vibration of the diaphragm will be inhibited by the voltages applied to the second capacitors while the direction is identified based on the voltages. The durability of the diaphragm can be improved.

Claims

1. A microphone comprising:

a diaphragm supported at a center thereof, and which vibrates when the diaphragm receives acoustic waves;

first electrode pairs, each of the first electrode pairs having a first electrode and a second electrode;

second electrode pairs, each of the second electrode pairs having a third electrode and a fourth electrode; and

a controller;

wherein;

the first electrodes are arranged on a surface of the diaphragm at positions distributed around the center of the diaphragm;

each of the second electrodes is arranged at a position facing a uniquely corresponding first electrode to form a gap between each of the second electrodes and the corresponding first electrode, each of the first electrode pairs forming a first capacitor;

the third electrodes are arranged on a surface of the diaphragm at positions distributed around the center of the diaphragm; and

each of the fourth electrodes is arranged at a position facing a uniquely corresponding third electrode to form a gap between each of the fourth electrodes and the corresponding third electrode,

each of the second electrode pairs forming a second capacitor;

the controller applies electric energy to each of the first capacitors and each of the second capacitors.

2. A microphone as in claim 1, wherein:

the controller applies predetermined electric energy to each of the first capacitors;

the controller detects the capacitance of each of the first capacitors;

the controller applies electric energy to each of the second capacitors, and each electric energy applied to the corresponding second capacitor is independently controlled such that the detected capacitance of each first capacitor is maintained at a constant value; and

the controller identifies a direction along which the acoustic wave propagates based on values of the electric energies, each electric energy being applied to each of the second capacitors.

3. A microphone as in claim 2, wherein the first electrode pairs are arranged on one side of the diaphragm, and the second electrode pairs are arranged on the other side of the diaphragm.

4. A microphone as in claim 2, wherein both of the first electrode pairs and the second electrode pairs are arranged on a same side of the diaphragm.

5. A microphone as in claim 2, wherein the controller identifies the direction from a phase difference between the electric energies, each electric energy being applied to each of the second capacitors.

6. A microphone as in claim 2, wherein:

the controller applies bias electric energy to each of the second capacitors so that the capacitances of the first capacitors are to be substantially equal to each other when the diaphragm does not vibrate;

the controller calculates a value subtracting a value of each bias electric energy from a value of the electric energy being applied to the corresponding second capacitor while the diaphragm vibrates; and

the controller identifies the direction from the calculated values.

7. A microphone as in claim 2, wherein the controller outputs electric signal corresponding to the electric energy being applied to one of the second capacitors when the identified direction is substantially equal to a predetermined direction.

8. A microphone as in claim 2, wherein the first electrode pairs are arranged on a circle around the center of the diaphragm at substantially equal intervals.

9. A microphone as in claim 2, wherein the second electrode pairs are arranged on a circle around the center of the diaphragm at substantially equal intervals.

10. A microphone as in claim 2, wherein the number of the first electrode pairs is same as the number of the second electrode pairs, each first electrode pair and corresponding second electrode pair being aligned when viewed along a direction perpendicular to the diaphragm.

11. A microphone as in claim 2, wherein the diaphragm has a substantially circular shape.

12. A microphone as in claim 2, wherein the center of the diaphragm and a periphery of the diaphragm are connected with a gimbal.

13. A microphone as in claim 1, wherein:

the first electrode pairs are arranged on one side of the diaphragm, and the second electrode pairs are arranged on the other side of the diaphragm;

the controller has a bridge circuit with the first capacitors and the second capacitors, the bridge circuit having a pair of input terminals and a pair of output terminals;

the controller applies predetermined electric energy to the first capacitors and the second capacitors via the pair of input terminals; and

the bridge circuit is formed so as to output electric signal via the pair of output terminals when the capacitances of the first capacitors change with substantially the same phase, the outputted electric signal corresponding to a change of capacitance of at least one of the first capacitors.

14. A microphone as in claim 13, wherein:

the first capacitors that are located within a half region of the diaphragm are connected in series between one input terminal of the bridge circuit and one output terminal of the bridge circuit;

the first capacitors that are located within the other half region of the diaphragm are connected in series between the other input terminal of the bridge circuit and the other output terminal of the bridge circuit;

the second capacitors that are located within the other half region of the diaphragm are connected in series between the one input terminal and the other output terminal; and

the second capacitors that are located within the half region of the diaphragm are connected in series between the other input terminal and the one output terminal.

15. A microphone as in claim 13, wherein the first electrode pairs are arranged on a circle around the center of the diaphragm at substantially equal intervals.

16. A microphone as in claim 13, wherein the second electrode pairs are arranged on a circle around the center of the diaphragm at substantially equal intervals.

17. A microphone as in claim 13, wherein the number of the first electrode pairs is same as the number of the second electrode pairs, each of the first electrode pairs and corresponding second electrode pair being aligned when viewed along a direction perpendicular to the diaphragm.

18. A microphone as in claim 13, wherein the diaphragm has a substantially circular shape in plane.

19. A microphone as in claim 13, wherein the center of the diaphragm and a periphery of the diaphragm are connected with a gimbal.

23. A method of manufacturing a microphone of claim 1, comprising:

forming a sacrifice layer on a surface of a semiconductor substrate so as to surround a predetermined region of the semiconductor substrate;

forming a semiconductor layer covering the sacrifice layer and the surrounded region of the semiconductor substrate; and

removing the sacrifice layer by etching.

24. A method as in claim 23, wherein the semiconductor layer is formed so as to leave an outer portion of the sacrifice layer exposed, and the method further comprises:

forming a second sacrifice layer that covers from the surface of the outer portion of the sacrifice layer to the surface of the semiconductor layer;

forming a backplate layer that covers from the surface of the semiconductor substrate surrounding the sacrifice layer to a position on the second sacrifice layer, the position facing at least a periphery of the semiconductor layer; and

removing the second sacrifice layer by etching.

20. A microphone comprising:

a diaphragm supported at the center thereof, and which vibrates when the diaphragm receives acoustic waves;

sensors distributed around the center of the diaphragm for detecting displacements of the diaphragm at the distributed positions;

actuators distributed around the center of the diaphragm for canceling the detected displacements; and

a controller identifying a direction along which the acoustic wave propagates based on values of electric energies applied to the actuators for canceling the displacements of the diaphragm during vibration.

21. A microphone comprising:

a diaphragm supported at the center thereof, and which vibrates with acoustic waves;

first sensors distributed on one side of the diaphragm around the center of the diaphragm, each first sensor outputting electric signal corresponding to a displacement of the diaphragm at a position facing the first sensor;

second sensors distributed on the other side of the diaphragm around the center of the diaphragm, each second sensor outputting electric signal corresponding to a displacement of the diaphragm at a position facing the second sensor; and

a bridge circuit electrically connecting the first sensors and the second sensors, wherein the bridge circuit is formed so as to output electric signal corresponding to the electric signal outputted from at least one of the first sensors when values of the electric signals outputted from the first sensors have a predetermined relationship.

22. A microphone as in claim 21, wherein the predetermined relationship is that the values of electric energies outputted from the first sensors have substantially same phase.