Spatial interference suppression using dual-microphone arrays

• US 9,485,574 B2
• Filed: 11/06/2015
• Issued: 11/01/2016
• Est. Priority Date: 12/13/2012
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Sun, Haohai, Moberg, Espen
• Primary Examiner(s): HOLDER, REGINA NEAL
• Application Number:
  US14/934,409
• Publication Number:
  US 20160066092A1
• Time in Patent Office: 361 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H04R 1/326 for microphones H04R1/34 and H04R1/40 take precedence
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2430/25 Array processing for suppression of unwanted side-lobes in directivity characteristics, e.g. a blocking matrix
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Systems, processes, devices, apparatuses, algorithms and computer readable medium for suppressing spatial interference using a dual microphone array for receiving, from a first microphone and a second microphone that are separated by a predefined distance, and that are configured to receive source signals, respective first and second microphone signals based on received source signals. A phase difference between the first and the second microphone signals is calculated based on the predefined distance. An angular distance between directions of arrival of the source signals and a desired capture direction is calculated based on the phase difference. Directional-filter coefficients are calculated based on the angular distance. Undesired source signals are filtered from an output based on the directional-filter coefficients.

Claims

1. A controller comprising:

an interface configured to receive signals from a first microphone and a second microphone;

a signal processor configured to;

calculate a phase difference between a first signal from a first microphone and a second signal from a second microphone, given a distance between the first microphone and the second microphone,

calculate directional-filter coefficients based on the phase difference,

obtain a plurality of directional-filter coefficients,

identify a subset of robust subband directional-filter coefficients from the plurality of directional-filter coefficients,

calculate a gain using an average of the subset of robust subband directional-filter coefficients, and

apply the gain to the plurality of directional-filter coefficients; and

a memory configured to store the gain to the plurality of directional-filter coefficients.

2. The controller of claim 1, further comprising:

an actuator configured to receive signals from the interface to position the first microphone and the second microphone.

3. The controller of claim 1, wherein the signal processor is configured to calculate an angular distance between directions of arrival of a desired direction and at least one of the first signal and the second signal, and the direction-filter coefficient is based on the angular distance.

4. The controller of claim 1, further comprising:

a display configured to display the phase difference, the angular distance, the directional-filter coefficients or the global gain.

5. The controller of claim 1, wherein the subset of robust subband directional-filter coefficients are associated with a frequency greater that 1 kilohertz (kHz).

6. The controller of claim 1, wherein the signal processor is configured to filter undesired source signals from an output of the signal processor based on the plurality of directional-filter coefficients.

7. The controller of claim 6, wherein the signal processor is configured to replace at least one of the plurality of directional-filter coefficients of a first range of subbands with an average value of the directional-filter coefficients for a second range of subbands.

8. The controller of claim 1, wherein the first range of frequency subbands corresponds with less than 1 kHz, and the second range of frequency subbands corresponds with at least 2 kHz.

9. The controller of claim 1, wherein the signal processor is configured to calculate phase differences, between the first signal and second signal, for a particular short-time frame, across a plurality of discrete subbands of the first signal and the second signal.

10. The controller of claim 1, wherein the signal processor is configured to calculate angular distances, for a particular short-time frame, across a plurality of discrete subbands of the first signal and the second signal, by applying a trigonometric function to phase differences calculated by the signal processor.

11. The controller of claim 10, wherein the signal processor is configured to calculate direction-filter coefficients, for a particular short-time frame, across a plurality of discrete subbands of the first signal and second signal, by applying a trigonometric function to angular distances calculated by the signal processor.

12. A computer implemented method comprising:

receiving, by an interface coupled to a signal processor, a first signal from a first microphone and a second signal from a second microphone;

calculating, by the signal processor, a phase difference between the first signal and the second signal, given a distance between the first microphone and the second microphone;

calculating, by the signal processor, an angular distance between a desired capture direction and one or more directions of arrival of at least one of the first signal and the second signal based on the phase difference;

calculating, by the signal processor, a plurality of directional-filter coefficients based on the angular distance;

calculating, by the signal processor, a gain using an average of robust subband directional-filter coefficients from the plurality of directional-filter coefficients; and

applying the average to the plurality of directional-filter coefficients.

13. The computer implemented method of claim 12, the method further comprising:

receiving, by an actuator, a control signal from the interface to control at least one of the first microphone and the second microphone.

14. The computer implemented method of claim 12, the method further comprising:

displaying, by a display, the phase difference, the angular distance, the directional-filter coefficients or the global gain.

15. The computer implemented method of claim 12, wherein the robust subband directional-filter coefficients corresponds with at least one frequency between 1 and 7 kHz.

16. The computer implemented method of claim 12, the method further comprising:

filtering, by the signal processor, undesired source signals from an output of the signal processor based on the plurality of directional-filter coefficients.

17. The computer implemented method of claim 16, the method further comprising:

replacing, by the signal processor, at least one of the directional-filter coefficients of a first range of subbands with an average value of the directional-filter coefficients for a second range of subbands.

18. The computer implemented method of claim 17, wherein the first range of frequency subbands corresponds to less than 1 kHz, and the second range of frequency subbands corresponds with at least 2 kHz.

19. The computer implemented method of claim 12, the method further comprising:

calculating, by the signal processor, phase differences, between the first and second microphone signals, for a particular short-time frame, across a plurality of discrete subbands of the first signal and the second signal.

20. A non-transitory computer readable medium including instructions stored in a memory and configured to be executed by a processor to:

calculate a phase difference between a first signal from a first microphone and a second signal from a second microphone based on a predefined distance of the first microphone and the second microphone;

calculate an angular distance between directions of arrival of source signals to the first and second microphones and a desired capture direction based on the phase difference;

calculate a plurality of directional-filter coefficients based on the angular distance;

calculate a gain using an average of robust subband directional-filter coefficients; and

apply the average globally to each of the plurality of directional-filter coefficients.