Method and system for detecting and mitigating audio howl in headsets

1. A method performed by a headset with a left headset housing and a right headset housing, the method comprising:

driving a speaker of the left headset housing with an audio signal;

determining whether audio howl is present within the left headset housing by comparing spectral content from a first error microphone signal produced by a first error microphone of the left headset housing and spectral content from a second error microphone signal produced by a second error microphone of the right headset housing; and

in response to determining that audio howl is present, filtering the audio signal to mitigate the audio howl.

2. The method of claim 1 further comprising generating the audio signal by filtering a reference microphone signal produced by a reference microphone of the left headset housing with an ambient sound enhancement (ASE) filter.

3. The method of claim 1 further comprising generating an anti-noise signal as the audio signal by filtering the first error microphone signal produced by the first error microphone.

4. The method of claim 3 further comprising

obtaining an input audio signal that contains user-desired audio content;

driving the speaker with a combination of the anti-noise signal and the input audio signal to produce sound, wherein the first error microphone is arranged to capture and convert the sound into the first error microphone signal; and

processing the first error microphone signal to remove sound of the input audio signal produced by the speaker to produce an error signal,

wherein the determination of whether audio howl is present is based on a comparison of spectral content from the error signal and spectral content from the second error microphone signal.

5. The method of claim 1 , wherein determining whether the audio howl is present comprises

generating, using the first error microphone signal, a first audio howl candidate that represents spectral content from the first error microphone signal over a frequency range;

comparing the first audio howl candidate with a second audio howl candidate representing spectral content from the second error microphone signal over the frequency range; and

determining whether the spectral content of the first audio howl candidate differs from the spectral content of the second audio howl candidate by a threshold.

6. The method of claim 5 further comprising obtaining, from the right headset housing, the second audio howl candidate.

7. The method of claim 5 further comprising

obtaining, from the right headset housing, the second error microphone signal; and

generating, using the second error microphone signal, the second audio howl candidate.

8. An in-ear headphone comprising:

a speaker of a first headphone housing;

a first error microphone of the first headphone housing;

a second error microphone of a second headphone housing;

a processor; and

memory having instructions which when executed by the processor causes the first in-ear headphone to:

drive the speaker with an audio signal;

determine whether audio howl is present within the first headphone housing by comparing spectral content from a first error microphone signal produced by the first error microphone and spectral content from a second error microphone signal produced by the second error microphone; and

in response to determining that audio howl is present, filter the audio signal to mitigate the audio howl.

9. The in-ear headphone of claim 8 further comprises a reference microphone of the first headphone housing, wherein the memory has further instructions to generate the audio signal by filtering a reference microphone signal produced by the reference microphone with an ambient sound enhancement (ASE) filter.

10. The in-ear headphone of claim 8 , wherein the memory has further instructions to generate an anti-noise signal as the audio signal by filtering the first error microphone signal produced by the first error microphone.

11. The in-ear headphone of claim 10 , wherein the memory has further instructions to

obtain an input audio signal that contains user-desired audio content;

drive the speaker with a combination of the anti-noise signal and the input audio signal to produce sound, wherein the first error microphone is arranged to capture and convert the sound into the first error microphone signal; and

process the first error microphone signal to remove sound of the input audio signal produced by the speaker to produce an error signal,

wherein the determination of whether audio howl is present is based on a comparison of spectral content from the error signal and spectral content from the second error microphone signal.

12. The in-ear headphone of claim 8 , wherein the instructions to determine whether the audio howl is present comprises instructions to

generate, using the first error microphone signal, a first audio howl candidate that represents spectral content from the first error microphone signal over a frequency range;

compare the first audio howl candidate with a second audio howl candidate representing spectral content from the second error microphone signal over a same frequency range; and

determine whether the spectral content of the first audio howl candidate differs from the spectral content of the second audio howl candidate by a threshold.

13. The in-ear headphone of claim 12 , wherein the memory has further instructions to obtain, from the second headphone housing, the second audio howl candidate.

14. The in-ear headphone of claim 12 , wherein the memory has further instructions to

obtain, from the second headphone housing, the second error microphone signal; and

generate, using the second error microphone signal, the second audio howl candidate.

15. A method performed by a headset with a left headset housing and a right headset housing, the method comprising:

driving a speaker of the left headset housing with an audio signal;

determining that audio howl is present within the left headset housing based on a comparison of spectral content from a first error microphone signal produced by a first error microphone of the left headset housing and spectral content from a second error microphone signal produced by a second error microphone of the right headset housing;

in response to determining that audio howl is present, determining whether a sound pressure level (SPL) of the spectral content from the first error microphone signal exceeds a threshold;

in response to the SPL exceeding the threshold

determining a band-limited filter with a gain reduction based on the SPL of the spectral content from the first error microphone signal; and

generating a filtered audio signal by filtering the audio signal with the band-limited filter.

16. The method of claim 15 , wherein the spectral content from the first error microphone signal is within a frequency range of the first error microphone signal, wherein the band-limited filter has a limit-band across the frequency range over which the gain reduction is applied to the audio signal.

17. The method of claim 15 , wherein, in response to the SPL being below the threshold, generating a filtered audio signal by applying a scalar gain to the audio signal.

18. The method of claim 15 , wherein the SPL is a first SPL, wherein determining that the audio howl is present comprises

generating, using the first error microphone signal, a first audio howl candidate that represents the spectral content from the first error microphone signal with the first SPL over a frequency range;

obtaining, from the right headset housing, a second audio howl candidate representing spectral content from the second error microphone signal with a second SPL over the frequency range; and

determining that the first SPL of the first audio howl candidate exceeds the second SPL of the second audio howl candidate by a candidate threshold.

19. The method of claim 18 , wherein the gain reduction of the band-limited filter is based on a difference between the first SPL and the threshold, and the band-limited filter has a limit-band across the frequency range over which the gain reduction is applied to the audio signal.

20. The method of claim 19 , wherein the band-limited filter is a first band-limited filter, the gain reduction is a first gain reduction, the limit-band is a first limit-band, and the frequency range is a first frequency range, wherein the method further comprises

generating, using the first error microphone signal, a third audio howl candidate that represents the spectral content from the first error microphone signal with a third SPL over a second, different frequency range;

obtaining, from the right headset housing, a fourth audio howl candidate representing spectral content from the second error microphone signal with a fourth SPL over the second frequency range;

in response to determining that the third SPL of the third audio howl candidate exceeds the fourth SPL of the fourth audio howl candidate by the candidate threshold, determining whether the third SPL exceeds the threshold; and

in response to the third SPL exceeding the threshold, determining a second band-limited filter with a second limit-band across a second frequency range over which a second gain reduction is to be applied to the audio signal,

wherein the filtered audio signal is generated by filtering the audio signal with the first and second band-limited filters.

21. The method of claim 20 , wherein the first frequency range and the first gain reduction of the first band-limited filter are different than the second frequency range and the second gain reduction of the second band-limited filter, respectively.