MICROPHONE TEST PROCEDURE

• US 20150010157A1
• Filed: 04/22/2014
• Published: 01/08/2015
• Est. Priority Date: 07/03/2013
• Status: Active Grant

• Current Assignee: Akustica Incorporated, Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Doller, Andrew J.
• Granted Patent: US 9,414,175 B2
• Time in Patent Office: Days
• US Class Current: 381/58
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 29/004 for microphones H04R29/007 takes precedence
• CPC Class Codes: H04R 29/006 Microphone matching
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

In one embodiment, the invention is a microphone system with an internal test circuit. The system includes a microphone having a housing with an acoustic port, a first transducer, a second transducer, a controller, and a current source. The system also includes an acoustic assembly with a cover and an acoustic pressure source positioned in the cover. When the acoustic assembly is positioned over the acoustic port, an acoustic chamber is formed, and a signal can be applied to the acoustic pressure source such that a first set of measurements can be taken. The acoustic assembly can be removed and replaced with an acoustic cover to take a second set of measurements. Based on the first and second measurements, sensitivities of the first and second transducers can be determined. In another embodiment, the invention provides a method for calibrating the sensitivity of a microphone.

Claims

1. A microphone test arrangement, comprising:

a microphone having

a housing,

an acoustic pressure source,

a first transducer,

a second transducer,

a controller, and

a current source;

wherein a first signal is applied to the acoustic pressure source and a first set of measurements are taken, and a second signal is applied to the one of the first transducer and the second transducer and a second set of measurements are taken; and

wherein a first sensitivity of the first transducer and a second sensitivity of the second transducer are determined from the first and second set of measurements.

2. The system of claim 1, further comprising,

the housing having an acoustic port;

the acoustic pressure source positioned in a cover, such that the acoustic pressure source and the cover comprise an acoustic pressure source assembly; and

an acoustic port cover;

wherein the acoustic pressure source assembly is positioned over the acoustic port forming an acoustic chamber, the first signal is applied to the acoustic pressure source and the first set of measurements are taken, the acoustic pressure source assembly is removed and the acoustic port cover is positioned over the acoustic port and the second set of measurements are taken.

3. The system of claim 1, wherein the acoustic pressure source comprises a third transducer.

4. The system of claim 3, wherein the acoustic pressure source further comprises a fourth transducer sharing a die with the third transducer, such that a first portion of the die comprises the third transducer and a second portion of the die comprises the fourth transducer.

5. The system of claim 1, wherein the first set of measurements includes measuring a voltage output by the first transducer in response to an acoustic pressure generated by the acoustic pressure source, and measuring a voltage output by the second transducer in response to the acoustic pressure.

6. The system of claim 1, wherein the second set of measurements includes measuring a voltage output by the second transducer when a current is applied to the first transducer.

7. The system of claim 6, wherein the current is applied to the first transducer by the current source.

8. The system of claim 7, wherein the current source is controlled by the controller.

9. The system of claim 1, further comprising a memory, wherein the first and second sensitivities are stored in the memory.

10. The system of claim 1, wherein the sensitivity of the first transducer is defined by the equation

11. The system of claim 10, wherein the sensitivity of the second transducer is defined by the equation

12. The system of claim 11, where the value of Z_ac is approximately equal to ±

1.

13. A method for calibrating a microphone, comprising:

generating an acoustic pressure in an acoustic chamber of the microphone;

measuring, by a controller, a voltage output by a first transducer of the microphone;

measuring, by a controller, a first voltage output by a second transducer of the microphone;

applying a current to the first transducer;

measuring, by a controller, a second voltage output by the second transducer; and

calculating a sensitivity of the first and second transducers based on the measurements.

14. The method of claim 13, further comprising

generating the acoustic pressure in the acoustic chamber, the acoustic chamber formed by an acoustic pressure assembly positioned over an acoustic port of the microphone,

removing the acoustic pressure assembly, and

covering the acoustic port.

15. The method of claim 13, further comprising generating the acoustic pressure source in the acoustic chamber, the acoustic chamber formed by a housing of the microphone.

16. The method of claim 13, wherein applying the current to the first transducer causes the first transducer to generate a pressure wave.

17. The method of claim 13, wherein the sensitivity of the first and second transducer is output to at least one of a memory and an input/output interface.

18. The method of claim 13, wherein the sensitivity of the first transducer is calculated using the equation

19. The method of claim 13, wherein the sensitivity of the second transducer is calculated using the equation

20. The method of claim 13, wherein the sensitivity of the first and second transducers are calculated with Z_ac=±

1.