REDUCING AN ACOUSTIC INTENSITY VECTOR WITH ADAPTIVE NOISE CANCELLATION WITH TWO ERROR MICROPHONES

• US 20140274198A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Miller, Antonio John
• Granted Patent: US 9,215,749 B2
• Time in Patent Office: Days
• US Class Current: 455/550.1
• 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 of a mobile phone, the first microphone facing a user;

receiving a second signal from a second microphone of the mobile phone, the second microphone facing the user; and

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

2. The method of claim 1, further comprising calculating an acoustic impedance based, at least in part, on the parameter proportional to the acoustic particle velocity.

3. The method of claim 2, further comprising determining a pressure applied by the user between the user and the mobile phone based, at least in part, on the acoustic impedance.

4. The method of claim 3, further comprising adjusting an active noise control algorithm based, at least in part, on the applied pressure.

5. The method of claim 4, further comprising detecting when the mobile phone is removed from the user'"'"'s ear.

6. The method of claim 4, further comprising:

calculating an acoustic intensity vector at the first microphone; and

adjusting the active noise control algorithm to reduce the acoustic intensity vector.

7. 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.

8. An apparatus, comprising:

a first error microphone facing a first direction;

a second error microphone facing the first direction; and

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

receiving a first signal from the first error microphone;

receiving a second signal from the second error microphone; and

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

9. The apparatus of claim 8, in which the first error microphone and the second error microphone are stacked.

10. The apparatus of claim 8, in which the processor is further configured to execute the step of calculating an acoustic impedance based, at least in part, on the parameter proportional to the acoustic particle velocity.

11. The apparatus of claim 10, in which the processor is further configured to execute the step of determining a pressure applied by the user between the user and the apparatus based, at least in part, on the acoustic impedance.

12. The apparatus of claim 11, in which the processor is further configured to execute the step of adjusting an active noise control algorithm based, at least in part, on the applied pressure.

13. The apparatus of claim 11, in which the processor is further configured to execute the step of detecting when the apparatus is removed from the user'"'"'s ear.

14. The apparatus of claim 13, in which the processor is further configured to execute the steps comprising:

calculating an acoustic intensity vector at the first microphone; and

adjusting the active noise control algorithm to reduce the acoustic intensity vector.

15. The apparatus of claim 8, 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.

16. The apparatus of claim 8, in which the processor is a digital signal processor.

17. 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; and

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

18. The computer program product of claim 17, in which the medium further comprises code to execute the steps comprising:

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

determining a pressure applied by the user between the user and a mobile phone, based at least in part, on the acoustic impedance.

19. The computer program product of claim 18, in which the medium further comprises code to execute the step of adjusting an active noise control algorithm based, at least in part, on the applied pressure.

20. The computer program product of claim 19, in which the medium further comprises code to execute the steps comprising:

calculating an acoustic intensity vector at the first microphone; and

adjusting the active noise control algorithm to reduce the acoustic intensity vector.