Systems and methods for sharing secondary path information between audio channels in an adaptive noise cancellation system

• US 9,704,472 B2
• Filed: 12/10/2013
• Issued: 07/11/2017
• Est. Priority Date: 12/10/2013
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Kwatra, Nitin
• Primary Examiner(s): Lee, Ping
• Application Number:
  US14/101,893
• Publication Number:
  US 20150161981A1
• Time in Patent Office: 1,309 Days
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2460/15 Determination of the acoustic seal of ear moulds or ear tips of hearing devices
• CPC Class Codes: H04R 25/00 Deaf-aid sets , i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception electrical stimulation of auditory nerves to promote the auditory function A61N1/36038; optical stimulation of auditory nerves to promote the auditory function A61N5/0622

Abstract

Systems and methods of the present disclosure include analyzing and comparing transfer functions associated with a plurality of electro-acoustic paths for transducers of a personal audio device to determine proximity of the transducers to respective ears of a listener of the personal audio device, quality of acoustic seals associated with the transducers, and for one or more other purposes.

Claims

1. An integrated circuit for implementing at least a portion of a personal audio device, comprising:

a first output for providing a first output signal to a first transducer including both a first source audio signal for playback to a listener and a first anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the first transducer;

a first error microphone input for receiving a first error microphone signal indicative of the output of the first transducer and the ambient audio sounds at the first transducer;

a second output for providing a second output signal to a second transducer including both a second source audio signal for playback to the listener and a second anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the second transducer;

a second error microphone input for receiving a second error microphone signal indicative of the output of the second transducer and the ambient audio sounds at the second transducer; and

a processing circuit that implements;

a first secondary path estimate adaptive filter for modeling an electro-acoustic path of the first source audio signal through the first transducer and having a response that generates a first secondary path estimate signal from the first source audio signal;

a first coefficient control block that shapes the response of the first secondary path estimate adaptive filter in conformity with the first source audio signal and a first playback corrected error by adapting the response of the first secondary path estimate filter to minimize the first playback corrected error, wherein the first playback corrected error is based on a difference between the first error microphone signal and the first secondary path estimate signal;

a second secondary path estimate adaptive filter for modeling an electro-acoustic path of the second source audio signal through the second transducer and having a response that generates a second secondary path estimate signal from the second source audio signal;

a second coefficient control block that shapes the response of the second secondary path estimate adaptive filter in conformity with the second source audio signal and a second playback corrected error by adapting the response of the second secondary path estimate filter to minimize the second playback corrected error, wherein the second playback corrected error is based on a difference between the second error microphone signal and the second secondary path estimate signal;

a first filter that generates the first anti-noise signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer based at least on the first playback corrected error;

a second filter that generates the second anti-noise signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer based at least on the second playback corrected error; and

a comparison block that compares the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter.

2. The integrated circuit of claim 1, wherein comparison of the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter is indicative of a proximity of each of the first transducer and the second transducer to a respective ear of the listener.

3. The integrated circuit of claim 1, wherein comparison of the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter is indicative of a quality of an acoustic seal between each of the first transducer and the second transducer to a respective ear of the listener.

4. The integrated circuit of claim 1, wherein the processing circuit is configured to alter, responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold, at least one of:

the first anti-noise signal, wherein such alteration is independent of a response of the first filter; and

the second anti-noise signal, wherein such alteration is independent of a response of the second filter.

5. The integrated circuit of claim 4, wherein the processing circuit is further configured to, responsive to altering the first-anti-noise signal in response to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold, resetting coefficients of the first coefficient control block to be substantially equal to those of the second coefficient control block.

6. The integrated circuit of claim 4, wherein the processing circuit is configured to attenuate at least one of the first anti-noise signal and the second anti-noise signal responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold.

7. The integrated circuit of claim 6, wherein attenuating at least one of the first anti-noise signal and the second anti-noise signal comprises muting at least one of the first anti-noise signal and the second anti-noise signal.

8. The integrated circuit of claim 6, further comprising:

a first reference microphone input for receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer; and

a second reference microphone input for receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer;

wherein;

the response of the first filter generates the first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer; and

the response of the second filter generates the second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

a first anti-noise path coefficient control block that shapes the response of the first filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first filter to minimize the ambient audio sounds in the first error microphone signal;

a second anti-noise path coefficient control block that shapes the response of the second filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second filter to minimize the ambient audio sounds in the second error microphone signal; and

further wherein the processing circuit is configured to;

freeze adaptation of the response of the first filter when the processing circuit attenuates the first anti-noise signal; and

freeze adaptation of the response of the second filter when the processing circuit attenuates the second anti-noise signal.

9. The integrated circuit of claim 1, further comprising:

a first reference microphone input for receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer; and

a second reference microphone input for receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer;

wherein;

the response of the first filter generates the first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer; and

the response of the second filter generates the second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

a first anti-noise path coefficient control block that shapes the response of the first filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first filter to minimize the ambient audio sounds in the first error microphone signal;

a second anti-noise path coefficient control block that shapes the response of the second filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second filter to minimize the ambient audio sounds in the second error microphone signal; and

further wherein the processing circuit is configured to reset coefficients of at least one of the first anti-noise path coefficient control block and the second anti-noise path coefficient control block to respective initial values responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold.

10. A method for canceling ambient audio sounds in the respective proximities of transducers associated with a personal audio device, the method comprising:

receiving a first error microphone signal indicative of an output of a first transducer and the ambient audio sounds at the first transducer;

receiving a second error microphone signal indicative of an output of a second transducer and the ambient audio sounds at the second transducer;

generating a first secondary path estimate signal from a first source audio signal by filtering the first source audio signal with a first secondary path estimate filter for modeling an electro-acoustic path of the first source audio signal through the first transducer, wherein a response of the first secondary path estimate adaptive filter is shaped in conformity with the first source audio signal and a first playback corrected error by adapting the response of the first secondary path estimate filter to minimize the first playback corrected error, wherein the first playback corrected error is based on a difference between the first error microphone signal and the first secondary path estimate signal;

generating a second secondary path estimate signal from a second source audio signal by filtering the second source audio signal with a second secondary path estimate filter for modeling an electro-acoustic path of the second source audio signal through the second transducer wherein a response of the second secondary path estimate adaptive filter is shaped in conformity with the second source audio signal and a second playback corrected error by adapting the response of the second secondary path estimate filter to minimize the second playback corrected error, wherein the second playback corrected error is based on a difference between the second error microphone signal and the second secondary path estimate signal;

generating a first anti-noise signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer based at least on the first playback corrected error;

generating a second anti-noise signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer based at least on the second playback corrected error; and

comparing the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter.

11. The method of claim 10, further comprising:

combining the first anti-noise signal with the first source audio signal to generate a first audio signal provided to the first transducer; and

combining the second anti-noise signal with the second source audio signal to generate a second audio signal provided to the second transducer.

12. The method of claim 10, wherein comparing the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter provides an indication of a proximity of each of the first transducer and the second transducer to a respective ear of a listener of the personal audio device.

13. The method of claim 10, wherein comparing the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter provides an indication of a quality of an acoustic seal between each of the first transducer and the second transducer to a respective ear of the listener.

14. The method of claim 10, further comprising altering, responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold, at least one of:

the first anti-noise signal, wherein such alteration is independent of a response of the first filter; and

the second anti-noise signal, wherein such alteration is independent of a response of the second filter.

15. The method of claim 14, further comprising, responsive to altering the first-anti-noise signal in response to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold, resetting coefficients of the first coefficient control block to be substantially equal to those of the second coefficient control block.

16. The method of claim 14, further comprising attenuating at least one of the first anti-noise signal and the second anti-noise signal responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold.

17. The method of claim 16, wherein attenuating at least one of the first anti-noise signal and the second anti-noise signal comprises muting at least one of the first anti-noise signal and the second anti-noise signal.

18. The method of claim 16, further comprising:

receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer; and

receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer;

wherein;

a response of a first filter generates the first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer; and

a response of a second filter generates the second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

shaping, by a first anti-noise path coefficient control block, the response of the first filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first filter to minimize the ambient audio sounds in the first error microphone signal, wherein adaptation of the response of the first filter is frozen during attenuation of the first anti-noise signal; and

shaping, by a second anti-noise path coefficient control block, the response of the second filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second filter to minimize the ambient audio sounds in the second error microphone signal, wherein adaptation of the response of the second filter is frozen during attenuation of the second anti-noise signal.

19. The method of claim 10, further comprising:

receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer; and

receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer;

wherein;

a response of a first filter generates the first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer; and

a response of a second filter generates the second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

shaping, by a first anti-noise path coefficient control block, the response of the first filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first filter to minimize the ambient audio sounds in the first error microphone signal;

shaping, by a second anti-noise path coefficient control block, the response of the second filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second filter to minimize the ambient audio sounds in the second error microphone signal; and

resetting coefficients of at least one of the first anti-noise path coefficient control block and the anti-noise path second coefficient control block to respective initial values responsive to the response of the first secondary path estimate adaptive filter and the response of the second secondary path estimate adaptive filter differing by more than a predetermined threshold.

20. An integrated circuit for implementing at least a portion of a personal audio device, comprising:

a first output for providing a first output signal to a first transducer including both a first source audio signal for playback to a listener and a first anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the first transducer;

a first error microphone input for receiving a first error microphone signal indicative of the output of the first transducer and the ambient audio sounds at the first transducer;

a first reference microphone input for receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer; and

a second output for providing a second output signal to a second transducer including both a second source audio signal for playback to the listener and a second anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the second transducer;

a second error microphone input for receiving a second error microphone signal indicative of the output of the second transducer and the ambient audio sounds at the second transducer;

a second reference microphone input for receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer; and

a processing circuit that implements;

a first adaptive filter that generates the first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer;

a second adaptive filter that generates the second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

a first coefficient control block that shapes the response of the first adaptive filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first adaptive filter to minimize the ambient audio sounds in the first error microphone signal;

a second coefficient control block that shapes the response of the second adaptive filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second adaptive filter to minimize the ambient audio sounds in the second error microphone signal; and

a comparison block that compares the response of the first adaptive filter and the response of the second adaptive filter.

21. The integrated circuit of claim 20, wherein the processing circuit is configured to alter, responsive to the response of the first adaptive filter and the response of the second adaptive filter differing by more than a predetermined threshold, at least one of:

the first anti-noise signal, wherein such alteration is independent of a response of the first adaptive filter; and

the second anti-noise signal, wherein such alteration is independent of a response of the second adaptive filter.

22. A method for canceling ambient audio sounds in the respective proximities of transducers associated with a personal audio device, the method comprising:

receiving a first error microphone signal indicative of an output of a first transducer and the ambient audio sounds at the first transducer;

receiving a second error microphone signal indicative of an output of a second transducer and the ambient audio sounds at the second transducer;

receiving a first reference microphone signal indicative of the ambient audio sounds at the acoustic output of the first transducer;

receiving a second reference microphone signal indicative of the ambient audio sounds at the acoustic output of the second transducer;

generating, by a first adaptive filter, a first anti-noise signal from the first reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the first transducer;

generating, by a second adaptive filter, a second anti-noise signal from the second reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output of the second transducer;

shaping, by a first anti-noise path coefficient control block, a response of the first filter in conformity with the first error microphone signal and the first reference microphone signal by adapting the response of the first filter to minimize the ambient audio sounds in the first error microphone signal;

shaping, by a second anti-noise path coefficient control block, a response of the second filter in conformity with the second error microphone signal and the second reference microphone signal by adapting the response of the second filter to minimize the ambient audio sounds in the second error microphone signal; and

comparing the response of the first adaptive filter and the response of the second adaptive filter.

23. The method of claim 22, further comprising altering, responsive to the response of the first adaptive filter and the response of the second adaptive filter differing by more than a predetermined threshold, at least one of:

the first anti-noise signal, wherein such alteration is independent of a response of the first adaptive filter; and

the second anti-noise signal, wherein such alteration is independent of a response of the second adaptive filter.