Noise mitigating microphone system and method

• US 8,351,632 B2
• Filed: 08/24/2009
• Issued: 01/08/2013
• Est. Priority Date: 08/23/2005
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Analog Devices, Inc.
• Inventors: Harney, Kieran P., Weigold, Jason, Elko, Gary
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): ROBINSON, RYAN C
• Application Number:
  US12/546,073
• Publication Number:
  US 20100054495A1
• Time in Patent Office: 1,233 Days
• Field of Search: 381/71.2, 381/71.9, 381/94.7, 381174-175, 381355-369, 381355-181
• US Class Current: 381/358
• CPC Class Codes: H04M 1/0214 Foldable telephones, i.e. with body parts pivoting to an open position around an axis parallel to the plane they define in closed position combined with translation movement H04M1/0235
• CPC Class Codes: H04M 1/03 Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets
• CPC Class Codes: H04M 1/035 Improving the acoustic characteristics by means of constructional features of the housing, e.g. ribs, walls, resonating chambers or cavities
• CPC Class Codes: H04M 1/19 Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor circuit arrangements for preventing eavesdropping H04M1/68; telephone cabinets E04H1/14
• CPC Class Codes: H04M 1/6008 in the transmitter circuit
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/245 of microphones
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• 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 system has a base coupled with first and second microphone apparatuses. The first microphone apparatus is capable of producing a first output signal having a noise component, while the second microphone apparatus is capable of producing a second output signal. The first microphone apparatus may have a first back-side cavity and the second microphone may have a second back-side cavity. The first and second back-side cavities may be fluidly unconnected. The system also has combining logic operatively coupled with the first microphone apparatus and the second microphone apparatus. The combining logic uses the second output signal to remove at least a portion of the noise component from the first output signal.

Claims

1. A microphone system comprising:

a base;

a first microphone apparatus coupled to the base, the first microphone apparatus capable of producing a first output signal having a noise component, the first microphone apparatus having a first variable capacitor formed on a substrate, the first variable capacitor and substrate defining a first back-side cavity;

a second microphone apparatus coupled to the base, the second microphone apparatus capable of producing a second output signal, the second microphone apparatus having a second variable capacitor formed on a substrate, the second variable capacitor and substrate defining a second back-side cavity, the first and second back-side cavities being fluidly unconnected; and

combining logic operatively coupled with the first microphone apparatus and the second microphone apparatus, the combining logic using the second output signal to remove at least a portion of the noise component from the first output signal,

the first microphone apparatus comprising a first microphone with a first low frequency cutoff, the second microphone apparatus comprising a second microphone with a second low frequency cutoff, the second low frequency cut-off being greater than the first low frequency cut-off,

the first microphone having a first diaphragm and a first circumferential gap defined at least in part by the first diaphragm, the second microphone having a second diaphragm and a second circumferential gap defined at least in part by the second diaphragm, the second circumferential gap being greater than the first circumferential gap.

2. The microphone system as defined by claim 1 wherein the second output signal comprises data relating to the mechanical response of the first microphone apparatus.

3. The microphone system as defined by claim 1 wherein the second microphone apparatus has a diaphragm and a cap acoustically sealing the diaphragm.

4. The microphone system as defined by claim 1 wherein the second microphone apparatus comprises a microphone and a low pass filter.

5. The microphone system as defined by claim 1 wherein the first microphone apparatus has a first microphone having first diaphragm, the second microphone apparatus having a second microphone with a second diaphragm, the first and second diaphragms being exposed to a common space.

6. The microphone system as defined by claim 1 wherein the second microphone apparatus includes a microphone and a signal transformation module.

7. The microphone as defined by claim 1 wherein the first microphone apparatus comprises a first microphone, the second microphone apparatus comprises a second microphone, the first microphone and second microphones having different air leakage rates for providing the first and second microphones with different low frequency cut-off points.

8. A microphone system comprising:

a base;

a first microphone apparatus coupled with the base and capable of producing a first output signal, the first microphone apparatus including a first microphone having a first mechanical response and a first variable capacitor formed on a substrate, the first variable capacitor and substrate defining a first back-side cavity;

a second microphone apparatus coupled with the base and capable of producing a second output signal, the second microphone apparatus including a second microphone having a second mechanical response and second variable capacitor formed on a substrate, the second variable capacitor and substrate defining a second back-side cavity, the first and second back-side cavities being fluidly unconnected; and

combining logic operatively coupled with the first microphone apparatus and the second microphone apparatus, the combining logic combining the first and second output signals to produce an output audio signal,

the first and second mechanical responses being effectively the same,

the first microphone having a first low frequency cutoff, the second microphone having a second low frequency cutoff, the second low frequency cut-off being greater than the first low frequency cut-off,

the first microphone having a first diaphragm and a first circumferential gap defined at least in part by the first diaphragm, the second microphone having a second diaphragm and a second circumferential gap defined at least in part by the second diaphragm, the second circumferential gap being greater than the first circumferential gap.

9. The microphone system as defined by claim 8 wherein the combining logic includes a subtractor that subtracts the second output signal from the first output signal.

10. The microphone system as defined by claim 8 further comprising means for removing audible response of mechanical shock from the first output signal.

11. The microphone system as defined by claim 8 wherein the second microphone apparatus comprises an adaptive filter.

12. The microphone system as defined by claim 8 wherein the first output signal comprises an audio component and a first noise component, the second output signal comprising a second noise component, the combining logic using the second noise component to mitigate the first noise component from the first output signal to produce the output audio signal.

13. A method of producing an output audio signal from a microphone system, the method comprising:

providing a base having a first microphone for generating a first microphone output signal in response to an input audio signal and a mechanical signal, the first microphone output signal having an audio component and a mechanical component, the base also having a second microphone for generating a second microphone output signal in response to the mechanical signal, the first microphone having a first variable capacitor formed on a substrate, the first variable capacitor and substrate defining a first back-side cavity, the second microphone having a second variable capacitor formed on a substrate, the second variable capacitor and substrate defining a second back-side cavity, the first and second back-side cavities being fluidly unconnected to one another; and

using information from the second microphone output signal to remove at least a portion of the mechanical component from the first microphone output signal,

the first microphone having a first low frequency cutoff, the second microphone having a second low frequency cutoff, the second low frequency cut-off being greater than the first low frequency cut-off,

the first microphone having a first diaphragm and a first circumferential gap defined at least in part by the first diaphragm, the second microphone having a second diaphragm and a second circumferential gap defined at least in part by the second diaphragm, the second circumferential gap being greater than the first circumferential gap.

14. The method as defined by claim 13 wherein the second microphone output signal has a second audio component, using comprising removing at least a portion of the second audio component from the second microphone output signal.

15. The method as defined by claim 13 further comprising fixed or adaptively filtering the second microphone output signal.

16. The method as defined by claim 15 wherein the second microphone output signal has a second audio component, using comprising removing at least a portion of the second audio component from the second microphone output signal before filtering.

17. The method as defined by claim 13 wherein the first microphone has a first diaphragm, the second microphone having a second diaphragm, the method exposing the first and second diaphragms to the input audio signal.