Portless and membrane-free microphone

Patent metadata

Field	Value
Publication number	US-10547953-B2
Application number	US-201515523631-A
Country	US
Kind code	B2
Filing date	Nov 9, 2015
Priority date	Nov 10, 2014
Publication date	Jan 28, 2020
Grant date	Jan 28, 2020

Abstract

Sound waves cause pressure changes in the air, and the pressure changes cause changes in the dielectric constant of air. Capacitive sensor measurements indicative of the changes in the dielectric constant of air can be processed to extract features associated with sound waves in the air. The features can include sound pressure levels represented and recordable as audio samples. Furthermore, the features can help identify types of sounds, determine direction of travel of the sound waves, and/or determine the source location of the audio. Instead of relying on movement of a mechanical member to transduce sound waves through a port into an electrical signal, an improved microphone uses capacitive sensing to directly sample and sense static pressure as well as dynamic pressure or pressure changes in the air to derive audio samples. The resulting microphone avoids disadvantages of the conventional microphone having the moving mechanical member and port.

First claim

What is claimed is:

1. A microphone for direct capacitive sensing of sound waves in the air, the microphone comprising:
a static capacitive sensor directly exposed to pressure changes in the air near the capacitive sensor, said static capacitive sensor having a sensing portion and a first signal trace for conducting an excitation signal to excite the static capacitive sensor; and
wherein:
the first signal trace is connected to first circuitry for taking a capacitive measurement of the air near the sensing portion; and

the first circuitry is connectable to second circuitry for processing the capacitive sensor measurement as an audio sample.

2. The microphone of claim 1 , wherein the capacitive measurement is indicative of a dielectric constant of the air near the sensing portion.

3. The microphone of claim 1 , wherein the capacitive measurement is indicative of a sound pressure level of the air near the sensing portion.

4. The microphone of claim 1 , wherein the static capacitive sensor does not include a moving member reactive to pressure changes in the air near the sensing portion to sense capacitance in the air near the sensing portion.

5. The microphone of claim 1 , wherein the microphone does not include or is not placed next to a porthole for directing sound waves to the sensing portion.

6. The microphone of claim 1 , wherein the sensing portion comprises a two-dimensional planar structure attached to the signal trace, said two-dimensional planar structure adapted to generate an electric field in response to the excitation signal and sense a change in capacitance in response to pressure changes in the air near the sensing portion.

7. The microphone of claim 1 , wherein the sensing portion comprises a two-dimensional planar structure having one or more cut-outs.

8. The microphone of claim 1 , wherein the sensing portion comprises a three-dimensional structure attached to the signal trace, said three-dimensional structure adapted to generate an electric field in response to the excitation signal and sense a change in capacitance in response to pressure changes in the air near the sensing portion.

9. The microphone of claim 1 , wherein the sensing portion comprises a three-dimensional structure having one or more cut-outs.

10. The microphone of claim 1 , wherein:
the static capacitive sensor further comprises a second signal trace alongside the first signal trace;
the second signal trace is not connected the sensing portion;
the second signal trace is connectable to the first circuitry; and
the first circuitry rejects a common mode signal present on the first signal trace and the second signal trace.

11. An audio sensing system for producing audio samples via direct capacitive sensing of air, the audio sensing system comprising:
a static capacitive sensor directly exposed to pressure changes in the air near the static capacitive sensor, said static capacitive sensor having a sensing portion and a signal trace for conducting an excitation signal to excite the static capacitive sensor;
first circuitry connectable to the capacitive sensor via the signal trace, said first circuitry for taking a capacitive sensor measurement of the air near the sensing portion; and
second circuitry connectable to the first circuitry for processing the capacitive sensor measurement as an audio sample.

12. The audio sensing system of claim 11 , wherein the first circuitry comprises a capacitance to digital converter.

13. The audio sensing system of claim 11 , wherein the first circuitry comprises an integrating amplifier for integrating a signal on the signal trace.

14. The audio sensing system of claim 13 , wherein the first circuitry comprises an analog-to-digital converter for converting the output of the integrating amplifier into a digital sample representative of the capacitive sensor measurement.

15. The audio sensing system of claim 11 , wherein the second circuitry stores the capacitive sensor measurement as an audio sample in a memory element.

16. A method for deriving audio samples via direct capacitive sensing of air, the method comprising:
exciting a static capacitive sensor using an excitation signal, wherein the capacitive sensor has sensing portion and a signal trace for conducting the excitation signal to the sensing portion, and the static capacitive sensor is directly exposed to pressure changes in the air near the sensing portion;
taking a capacitive measurement of the air near the sensing portion; and
processing the capacitive measurement as an audio sample.

17. The method of claim 16 , wherein the capacitive measurement is indicative of at least one of a dielectric constant and sound pressure level of the air near the sensing portion.

18. The method of claim 16 , wherein taking the capacitive measurement of the air near the sensing portion comprises:
integrating using an integrating amplifier a signal on the signal trace of the static capacitive sensor.

19. The method of claim 18 , wherein taking the capacitive measurement of the air near the sensing portion further comprises:
providing an output of the integrating amplifier to an analog-to-digital converter for converting the output of the integrating amplifier into a digital sample representative of the capacitive measurement.

20. The method of claim 16 , wherein processing the capacitive measurement as the audio sample comprises storing the capacitive measurement as the audio sample in a memory element.

Assignees

• Analog Devices Inc

Inventors

• Wingate David
• Novet Isaac Chase

Classifications

• H04R19/04 Primary

  Microphones (H04R19/01 takes precedence) · CPC title

• H04R3/06

  of electrostatic transducers · CPC title

• A61B2562/0204

  Acoustic sensors · CPC title

• H04R23/006

  using solid state devices (solid state devices per se H10) · CPC title

• G01L9/12

  by making use of variations in capacitance {, i.e. electric circuits therefor} · CPC title