Reducing an acoustic intensity vector with adaptive noise cancellation with two error microphones

• US 9,215,749 B2
• Filed: 03/14/2013
• Issued: 12/15/2015
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Miller, Antonio John
• Primary Examiner(s): CHIN, VIVIAN C
• Assistant Examiner(s): Kurr, Jason R
• Application Number:
  US13/828,823
• Publication Number:
  US 20140274198A1
• Time in Patent Office: 1,006 Days
• Field of Search: 381/71.1, 381/71.2, 381/71.3, 381/71.6, 381/71.7, 381/71.11, 381/71.12, 381/26, 381/57, 381/91, 381/92, 381/122, 455/550.1, 455/569.1, 455/570
• US Class Current: 1/1
• CPC Class Codes: G10K 11/17821 characterised by the analysis of the input signals only
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/1783 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A second error microphone may be incorporated in a mobile device to allow computation of additional parameters for modifying an adaptive noise cancellation (ANC) algorithm. For example, a first and second acoustic pressure may be calculated from a first and second error microphone of the mobile device. The first and second acoustic pressure may be input to an algorithm for determining an acoustic intensity vector. The ANC algorithm may receive the acoustic intensity vector as an input, and adapt an anti-noise signal to reduce the acoustic intensity vector. Additionally, an input impedance for the error microphones may be calculated from the acoustic pressure to determine coupling between a speaker and a user'"'"'s ear. The anti-noise algorithm may be adjusted or disabled when the input impedance indicates the user has removed the phone from the user'"'"'s ear.

Claims

1. A method, comprising:

receiving a first signal from a first microphone, the first microphone facing a user;

receiving a second signal from a second microphone, the second microphone facing the user;

calculating a parameter proportional to acoustic particle velocity based, at least in part, on the first signal and the second signal;

calculating an acoustic intensity vector based, at least in part, on the calculated parameter proportional to the acoustic particle velocity;

adjusting an audio output signal for output to a transducer based, at least in part, on the calculated acoustic intensity vector, wherein the step of adjusting the audio output signal comprises adjusting an active noise control algorithm to reduce the acoustic intensity vector;

calculating an acoustic impedance based, at least in part, on the calculated parameter proportional to the acoustic particle velocity; and

disabling the active noise control algorithm when the determined acoustic impedance indicates the device is removed from the user'"'"'s ear.

2. The method of claim 1, further comprising:

determining a pressure applied between the device and the user'"'"'s ear based, at least in part, on the calculated acoustic impedance;

adjusting the active noise control algorithm based, at least in part, on the applied pressure.

3. The method of claim 2, further comprising detecting when the device is removed from the user'"'"'s ear based, at least in part, on the determined pressure.

4. The method of claim 1, further comprising:

calculating a first acoustic pressure at the first microphone based on the first signal; and

calculating a second acoustic pressure at the second microphone based on the second signal,

in which the calculated parameter is based, at least in part, on the first acoustic pressure and the second acoustic pressure.

5. An apparatus, comprising:

a first error microphone facing a first direction;

a second error microphone facing the first direction; and

a transducer;

a processor coupled to the first error microphone, coupled to the second error microphone, and coupled to the transducer, wherein the processor is configured to execute the steps comprising;

receiving a first signal from the first error microphone;

receiving a second signal from the second error microphone;

calculating a parameter proportional to acoustic particle velocity based, at least in part, on the first signal and the second signal;

calculating an acoustic intensity vector based, at least in part, on the calculated parameter proportional to the acoustic particle velocity;

adjusting an audio output signal provided to the transducer based, at least in part, on the calculated acoustic impedance intensity vector, wherein the step of adjusting the audio output signal comprises adjusting an active noise control algorithm to reduce the acoustic intensity vector;

calculating an acoustic impedance based, at least in part, on the calculated parameter proportional to the acoustic particle velocity; and

disabling the active noise control algorithm when the determined acoustic impedance indicates the device is removed from a user'"'"'s ear.

6. The apparatus of claim 5, in which the first error microphone and the second error microphone are stacked.

7. The apparatus of claim 5, in which the processor is further configured to execute a step of determining a pressure applied by a user between the user and the apparatus based, at least in part, on the acoustic impedance.

8. The apparatus of claim 7, in which the processor is further configured to execute a step of adjusting the active noise control algorithm based, at least in part, on the applied pressure.

9. The apparatus of claim 8, in which the processor is further configured to execute a step of detecting when the apparatus is removed from the user'"'"'s ear based, at least in part, on the determined pressure.

10. The apparatus of claim 5, in which the processor is further configured to execute the steps comprising:

calculating a first acoustic pressure at the first microphone based, at least in part, on the first signal; and

calculating a second acoustic pressure at the second microphone based, at least in part, on the second signal,

in which the calculated parameter is based, at least in part, on the first acoustic pressure and the second acoustic pressure.

11. The apparatus of claim 5, in which the processor is a digital signal processor.

12. A computer program product, comprising:

a non-transitory computer readable medium comprising code to execute the steps comprising;

receiving a first signal from a first microphone facing a user;

receiving a second signal from a second microphone facing the user;

calculating a parameter proportional to acoustic particle velocity based, at least in part, on the first signal and the second signal;

calculating an acoustic intensity vector based, at least in part, on the parameter proportional to the acoustic particle velocity; and

adjusting an audio output signal provided to a transducer based, at least in part, on the calculated acoustic intensity vector, wherein the step of adjusting the audio output signal comprises adjusting an active noise control algorithm to reduce the acoustic intensity vector;

calculating an acoustic impedance based, at least in part, on the calculated parameter proportional to the acoustic particle velocity; and

disabling the active noise control algorithm when the determined acoustic impedance indicates the device is removed from the user'"'"'s ear.

13. The computer program product of claim 12, in which the medium further comprises code to execute the step of

determining a pressure applied by a user between the user and a device containing the transducer, based at least in part, on the acoustic impedance.

14. The computer program product of claim 13, in which the medium further comprises code to execute the step of adjusting the active noise control algorithm based, at least in part, on the applied pressure.

15. An apparatus, comprising:

a first input node configured to receive a first signal from a first error microphone;

a second input node configured to receive a second signal from a second error microphone;

an output node configured to output an audio output signal for output to a transducer;

a processor coupled to the first input node, to the second input node, and to the output node, wherein the processor is configured to execute the steps comprising;

calculating a parameter proportional to acoustic particle velocity based, at least in part, on the first signal and the second signal;

calculating an acoustic intensity vector based, at least in part, on the calculated parameter proportional to the acoustic particle velocity;

adjusting the audio output signal provided to the transducer based, at least in part, on the calculated acoustic intensity vector, wherein the step of adjusting the audio output signal comprises adjusting an active noise control algorithm to reduce the acoustic intensity vector;

calculating an acoustic impedance based, at least in part, on the calculated parameter proportional to the acoustic particle velocity; and

disabling the active noise control algorithm when the determined acoustic impedance indicates the device is removed from a user'"'"'s ear.

16. The apparatus of claim 15, in which the processor is further configured to execute a step of determining a pressure applied by a user between the user and the apparatus based, at least in part, on the calculated acoustic impedance.

17. The apparatus of claim 16, in which the processor is further configured to execute a step of adjusting the active noise control algorithm based, at least in part, on the applied pressure.

18. The apparatus of claim 17, in which the processor is further configured to execute a step of detecting when the apparatus is removed from the user'"'"'s ear based, at least in part, on the determined pressure.

19. The apparatus of claim 15, in which the processor is further configured to execute the steps comprising:

calculating a first acoustic pressure at the first microphone based, at least in part, on the first signal; and

calculating a second acoustic pressure at the second microphone based, at least in part, on the second signal,

in which the calculated parameter is based, at least in part, on the first acoustic pressure and the second acoustic pressure.