Active noise cancelation with controllable levels

Patent metadata

Field	Value
Publication number	US-10049653-B2
Application number	US-201615570273-A
Country	US
Kind code	B2
Filing date	Oct 14, 2016
Priority date	Oct 16, 2015
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A system including an automatic noise canceling (ANC) headphone and a processor. The ANC headphone has a microphone configured to generate a microphone signal and at least two non-zero ANC gain levels. The processor is configured to receive the microphone signal, determine a characteristic of the microphone signal, identify a revised ANC level from the ANC gain levels based on a comparison of the characteristic to at least one threshold, and output a signal corresponding to the revised ANC level. Methods are also disclosed.

First claim

The invention claimed is:

1. A system comprising:
an automatic noise canceling (ANC) headphone having an ANC feedforward microphone configured to generate a feedforward microphone signal, the ANC headphone further having ANC gain levels including at least two non-zero ANC gain levels; and
a processor configured to receive the feedforward microphone signal, determine a characteristic of the feedforward microphone signal, compare the characteristic to at least one threshold, select one of the ANC gain levels based on the comparison of the characteristic to the at least one threshold, and output a signal corresponding to the selected ANC gain level.

2. The system of claim 1 , in which the ANC gain levels are feedforward ANC gain levels.

3. The system of claim 1 , in which the processor includes:
a first bandpass filter having a first center frequency and
a second bandpass filter having a second center frequency that is greater than the first center frequency,
in which the first bandpass filter is configured to filter a low-frequency range of the feedforward microphone signal,
in which the second bandpass filter is configured to filter a mid-frequency range of the feedforward microphone signal, and
in which the determined characteristic includes a power value of the low-frequency range of the feedforward microphone signal and a power value of the mid-frequency range of the feedforward microphone signal.

4. The system of claim 3 , in which the first bandpass filter has a passband of about 20 Hz to about 600 Hz, and in which the second bandpass filter has a passband of about 500 Hz to about 2500 Hz.

5. The system of claim 3 , in which the processor is configured to select one of the ANC gain levels based on a comparison of the power value of the low-frequency range to a first threshold and the power value of the mid-frequency range to a second threshold that is not equal to the first threshold.

6. The system of claim 3 , in which the processor further includes a moving-window mean-square estimator configured to determine the power value of the low-frequency range of the feedforward microphone signal and the power value of the mid-frequency range of the feedforward microphone signal.

7. The system of claim 1 , in which the ANC gain levels include a soft-gain level and a strong-gain level that is greater than the soft-gain level.

8. The system of claim 7 , further comprising an audio speaker, in which the processor is further configured to detect whether audio is being played by the audio speaker and, when audio is being played, to output a signal corresponding to the strong-gain level.

9. The system of claim 7 , in which the ANC gain levels include a mid-gain level that is greater than the soft-gain level and less than the strong-gain level.

10. The system of claim 1 , in which the processor is further configured to feather an anti-noise signal between an off state and at least one of the ANC gain levels and also to feather the anti-noise signal between a first level of the ANC gain levels and a second level of the ANC gain levels.

11. The system of claim 10 , in which the feathered anti-noise signal includes a feedforward anti-noise signal and a feedback anti-noise signal.

12. The system of claim 10 , in which the feathered anti-noise signal includes a feedback anti-noise signal and not a feedforward anti-noise signal.

13. The system of claim 10 , further comprising:
a first controllable gain between a feedforward anti-noise signal path and a feedback anti-noise signal path; and
a second controllable gain between the feedforward anti-noise signal path and an output side of a feathered gain mixer, in which the first controllable gain is configured to selectively permit a feedforward anti-noise signal to pass from the feedforward anti-noise signal path to the feedback anti-noise signal path at an input side of the feathered gain mixer, and in which the second controllable gain is configured to selectively permit the feedforward anti-noise signal to pass from the feedforward anti-noise signal path to the output side of the feathered gain mixer.

14. The system of claim 1 , in which the processor is further configured to match the selected ANC gain level to a predetermined audio equalizer (EQ) profile.

15. The system of claim 1 , in which the output signal includes a request to increase or decrease an initial ANC gain level to one of the ANC gain levels.

16. A method of reducing automatic noise canceling (ANC) hiss in a headphone having an ANC system, the method comprising:
generating a feedforward microphone signal from an ANC feedforward microphone;
determining whether a noise floor of an ANC noise level exceeds an ambient noise level of the feedforward microphone for a frequency range; and,
if so, reducing a feedforward ANC gain of the ANC system for the frequency range until the ANC noise level is less than the ambient noise level for the frequency range.

17. The method of claim 16 , in which the feedforward ANC gain may be reduced from an initial gain level to one of a plurality of feedforward ANC gain levels.

18. The method of claim 17 , in which the plurality of feedforward ANC gain levels include a mid-gain level and a soft-gain level.

19. The method of claim 18 , in which the initial gain level is about five decibels greater than the mid-gain level, and in which the mid-gain level is about five decibels greater than the soft-gain level.

20. A method of revising an automatic noise canceling (ANC) gain level in an ANC headphone by a processor linked to the ANC headphone, the method comprising:
receiving a feedforward microphone signal from a feedforward microphone of the ANC headphone having ANC gain levels including at least two non-zero ANC gain levels;
determining a characteristic of the feedforward microphone signal;
comparing the characteristic to at least one threshold;
selecting one of the ANC gain levels based on the comparison of the characteristic to the at least one threshold; and
outputting a signal corresponding to the selected ANC gain level.

21. The method of claim 20 , in which the feedforward microphone signal from the feedforward microphone of the ANC headphone includes at least two non-zero feedforward ANC gain levels.

22. The method of claim 20 , in which the determining the characteristic of the microphone signal includes determining a power value of a low-frequency range of the feedforward microphone signal and a power value of a mid-frequency range of the feedforward microphone signal, the low-frequency range having a median frequency that is less than a median frequency of the mid-frequency range.

23. The method of claim 22 , in which the selecting one of the ANC gain levels based on the comparison of the characteristic to the at least one threshold includes selecting one of the ANC gain levels based on a comparison of the power value of the low-frequency range to a first threshold and the power value of the mid-frequency range to a second threshold that is not equal to the first threshold.

24. The method of claim 20 , in which the ANC gain levels include a soft-gain level, a mid-gain level that is greater than the soft-gain level, and a strong-gain level that is greater than the mid-gain level, the method further comprising:
detecting whether audio is being played by an audio speaker of the ANC headphone, and
outputting a signal corresponding to the strong-gain level when audio is being played.

Assignees

• Avnera Corp

Inventors

• Kumar Amit
• Sorensen Eric

Classifications

• G10K2210/3026

  Feedback · CPC title

• G10K2210/3014

  Adaptive noise equalizers [ANE], i.e. where part of the unwanted sound is retained · CPC title

• G10K2210/3027

  Feedforward · CPC title

• G10K2210/1081

  Earphones, e.g. for telephones, ear protectors or headsets · CPC title

• G10K2210/3028

  Filtering, e.g. Kalman filters or special analogue or digital filters · CPC title