Robust and reliable acoustic echo and noise cancellation system for cabin communication

• US 7,171,003 B1
• Filed: 10/19/2000
• Issued: 01/30/2007
• Est. Priority Date: 10/19/2000
• Status: Expired due to Fees

• Current Assignee: Lear Corporation
• Original Assignee: Lear Corporation
• Inventors: Finn, Alan M., Venkatesh, Saligrama R.
• Primary Examiner(s): Mei; Xu
• Application Number:
  US09/692,531
• Time in Patent Office: 2,294 Days
• Field of Search: 381/86, 381/71.1, 381/71.2, 381/71.4, 381/71.7, 381/71.8, 381/71.11, 381/71.18, 381/59, 381/58, 381/94.1, 379/406.01, 379/406.02, 379/406.03, 379/406.08, 379/406.15
• US Class Current: 381/66
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

A cabin communication system for improving clarity of a voice spoken within an interior cabin having ambient noise includes an adaptive speech enhancement filter for receiving an audio signal that includes a first component indicative of the spoken voice, a second component indicative of a feedback echo of the spoken voice and a third component indicative of the ambient noise, the speech enhancement filter filtering the audio signal by removing the third component to provide a filtered audio signal, the speech enhancement filter adapting to the audio signal at a first adaptation rate, and an adaptive acoustic echo cancellation system for receiving the filtered audio signal and removing the second component in the filtered audio signal to provide an echo-cancelled audio signal, the echo cancellation signal adapting to the filtered audio signal at a second adaption rate, wherein the first adaptation rate and the second adaptation rate are different from each other so that the speech enhancement filter does not adapt in response to operation of the echo-cancellation system and the echo-cancellation system does not adapt in response to operation of the speech enhancement filter.

Claims

1. A cabin communication system for improving clarity of a voice spoken within an interior cabin having ambient noise, said cabin communication system comprising:

an adaptive speech enhancement filter for receiving an audio signal that includes a first component indicative of the spoken voice, a second component indicative of a feedback echo of the spoken voice and a third component indicative of the ambient noise, said speech enhancement filter filtering the audio signal by removing the third component to provide a filtered audio signal, said speech enhancement filter adapting to the audio signal at a first adaptation rate;

an adaptive acoustic echo cancellation system for receiving the filtered audio signal and removing the second component in the filtered audio signal to provide an echo-cancelled audio signal, said echo cancellation system adapting to the filtered audio signal at a second adaptation rate; and

random noise adding means for adding random noise to the filtered audio signal, said echo cancellation system using the filtered audio signal with the random noise added thereto to identify the second component, wherein the random noise is a dither signal, and wherein the cabin is movable at a variable velocity and the dither signal is scaled to the velocity;

wherein said first adaptation rate and said second adaptation rate are different from each other so that said speech enhancement filter does not adapt in response to operation of said echo-cancellation system and said echo-cancellation system does not adapt in response to operation of said speech enhancement filter.

2. The cabin communication system of claim 1, wherein said first adaptation rate is greater than said second adaptation rate.

3. The cabin communication system of claim 2, wherein said first adaptation rate of said speech enhancement filter is controlled by a step size β

, wherein said second adaptation rate of said echo cancellation system is controlled by a step size μ

, and wherein β

is much less than μ

.

4. The cabin communication system of claim 3, wherein said audio signal is sampled at a sampling frequency F_s, wherein n is the number of samples of the audio signal accumulated for block processing by said speech enhancement filter, wherein said echo cancellation system includes a plurality of filters and a variable 1/k is the fraction of said plurality of filters that are updated each sampling period, and wherein:

5. The cabin communication system of claim 1, wherein said first adaptation rate is an adaptation rate of a long term noise estimate by said speech enhancement filter, said first adaptation rate being much smaller than said second adaptation rate, and said second adaptation rate being much smaller than a basic filter rate of said speech enhancement filter.

6. A cabin communication system for improving clarity of a voice spoken within an interior cabin having ambient noise, said cabin communication system comprising:

an adaptive speech enhancement filter for receiving an audio signal that includes a first component indicative of the spoken voice, a second component indicative of a feedback echo of the spoken voice and a third component indicative of the ambient noise, said speech enhancement filter filtering the audio signal by removing the third component to provide a filtered audio signal; and

an adaptive acoustic echo cancellation system for receiving the filtered audio signal and removing the second component in the filtered audio signal to provide an echo-cancelled audio signal,

wherein said speech enhancement filter and said echo cancellation system are coupled,

wherein said cabin communication performs a coupled on-line identification of noise and echoes in the audio signal to effect closed loop control of the adaptations of said speech enhancement filter and said echo cancellation system,

wherein said speech enhancement filter adapts to the audio signal at a first adaptation rate and said echo cancellation system adapts to the filtered audio signal at a second adaptation rate, and wherein said first adaptation rate is greater than said second adaptation rate so that said speech enhancement filter does not adapt in response to operation of said echo cancellation system and said echo cancellation system does not adapt in response to operation of said speech enhancement filter,

wherein said first adaptation rate of said speech enhancement filter is controlled by a step size β

, wherein said second adaptation rate of said echo cancellation system is controlled by a step size μ

, and wherein β

is much less than μ

, and

wherein said audio signal is sampled at a sampling frequency F_s, wherein n is the number of samples of the audio signal accumulated for block processing by said speech enhancement filter, wherein said echo cancellation system includes a plurality of filters and a variable 1/k is the fraction of said plurality of filters that are updated each sampling period, and wherein;

7. The cabin communication system of claim 6, wherein said first adaptation rate is an adaptation rate of a long term noise estimate by said speech enhancement filter, said first adaptation rate being much smaller than said second adaptation rate, and said second adaptation rate being much smaller than a basic filter rate of said speech enhancement filter.

8. The cabin communication system of claim 6, further comprising random noise adding means for adding random noise to the filtered audio signal, said echo cancellation system using the filtered audio signal with the random noise added thereto to identify the second component.

9. The cabin communication system of claim 8, wherein the random noise is a dither signal.

10. The cabin communication system of claim 9, wherein the cabin is movable at a variable velocity and the dither signal is scaled to the velocity.

11. A cabin communication system for improving clarity of a voice spoken within an interior cabin having ambient noise, said cabin communication system comprising:

a microphone for receiving the spoken voice and the ambient noise and for converting the spoken voice and the ambient noise into a first audio signal, the first audio signal having a first component corresponding to the spoken voice and a second component corresponding to the ambient noise;

an adaptive speech enhancement filter for filtering the first audio signal by removing the second component to provide a filtered audio signal, said speech enhancement filter adapting to the first audio signal at a first adaptation rate;

an adaptive acoustic echo cancellation system for receiving the filtered audio signal and providing an echo-cancelled audio signal, said echo cancellation signal adapting to the filtered audio signal at a second adaptation rate; and

a loudspeaker for converting the echo-cancelled audio signal into an output reproduced voice within the cabin including a third component indicative of the first audio signal,

wherein said loudspeaker and said microphone are acoustically coupled so that the output reproduced voice is fed back from said loudspeaker to be received by said microphone and converted with the spoken voice into the first audio signal,

wherein said echo cancellation system removes from the filtered audio signal any portion of the filtered audio signal corresponding to the third component,

wherein said first adaptation rate is greater than said second adaptation rate so that said speech enhancement filter does not adapt in response to operation of said echo-cancellation system and said echo-cancellation system does not adapt in response to operation of said speech enhancement filter,

wherein said first adaptation rate of said speech enhancement filter is controlled by a step size β

, wherein said second adaptation rate of said echo cancellation system is controlled by a step size μ

, and wherein β

is much less than μ

, and

wherein said first audio signal is sampled at a sampling frequency F_s, wherein n is the number of samples of the first audio signal accumulated for block processing by said speech enhancement filter, wherein said echo cancellation system includes a plurality of filters and a variable 1/k is the fraction of said plurality of filters that are updated each sampling period, and wherein;

12. The cabin communication system of claim 11, wherein said first adaptation rate is an adaptation rate of a long term noise estimate by said speech enhancement filter, said first adaptation rate is much smaller than said second adaptation rate, and said second adaptation rate is much smaller than a basic filter rate of said speech enhancement filter.

13. The cabin communication system of claim 11, further comprising random noise adding means for adding random noise to the filtered audio signal, said echo cancellation system using the filtered audio signal with the random noise added thereto to identify the third component.

14. The cabin communication system of claim 13, wherein the random noise is a dither signal.

15. The cabin communication system of claim 14, wherein the cabin is movable at a variable velocity and the dither signal is scaled to the velocity.

16. A method for improving clarity of a voice spoken within an interior cabin having ambient noise, said method comprising the steps of:

adaptively filtering, for speech enhancement, an audio signal that includes a first component indicative of the spoken voice, a second component indicative of a feedback echo of the spoken voice and a third component indicative of the ambient noise, said filtering step removing the third component to provide a filtered audio signal, said filtering step adapting to the audio signal at a first adaptation rate; and

adaptively processing the filtered audio signal to remove the second component by acoustic echo cancellation to provide an echo-cancelled audio signal, said processing step adapting to the filtered audio signal at a second adaptation rate,

wherein said first adaptation rate is greater than said second adaptation rate so that said filtering step does not adapt in response to operation of said processing step and said processing step does not adapt in response to operation of said filtering step,

wherein said first adaptation rate of said filtering step is controlled by a step size β

, wherein said second adaptation rate of said processing step is controlled by a step size μ

, and wherein β

is much less than μ

, and

wherein the first audio signal is sampled at a sampling frequency F_s, wherein n is the number of samples of the first audio signal accumulated for block processing by said speech enhancement filter, wherein said processing step uses a plurality of filters and a variable 1/k is the fraction of the plurality of filters that are updated each sampling period, and wherein;

17. The method of claim 16, wherein said first adaptation rate is an adaptation rate of a long term noise estimate by said filtering step, said first adaptation rate being much smaller than said second adaptation rate, and said second adaptation rate being much smaller than a basic filter rate of said filtering step.

18. The method of claim 16, further comprising the step of adding random noise to the filtered audio signal, processing step using the filtered audio signal with the random noise added thereto to identify the second component.

19. The method of claim 18, wherein the random noise is a dither signal.

20. The method of claim 19, wherein the cabin is movable at a variable velocity and the dither signal is scaled to the velocity.

21. A movable vehicle cabin having ambient noise, said cabin comprising:

means for causing movement of said cabin, wherein at least a portion of the ambient noise during movement is a result of the movement; and

a cabin communication system for improving clarity of a voice spoken within an interior of said cabin, wherein said cabin communication system comprises;

a microphone for receiving the spoken voice and the ambient noise and for converting the spoken voice and the ambient noise into a first audio signal, the first audio signal having a first component corresponding to the spoken voice and a second component corresponding to the ambient noise;

an adaptive speech enhancement filter for filtering the first audio signal by removing the second component to provide a filtered audio signal, said speech enhancement filter adapting to the first audio signal at a first adaptation rate;

an adaptive acoustic echo cancellation system for receiving the filtered audio signal and providing an echo-cancelled audio signal, said echo cancellation system adapting to the filtered audio signal at a second adaptation rate; and

a loudspeaker for converting the echo-cancelled audio signal into an output reproduced voice within the cabin including a third component indicative of the first audio signal,

wherein said loudspeaker and said microphone are acoustically coupled so that the output reproduced voice is fed back from said loudspeaker to be received by said microphone and converted with the spoken voice into the first audio signal,

wherein said echo cancellation system removes from the filtered audio signal any portion of the filtered audio signal corresponding to the third component,

wherein said first adaptation rate is greater than said second adaptation rate so that said speech enhancement filter does not adapt in response to operation of said echo-cancellation system and said echo-cancellation system does not adapt in response to operation of said speech enhancement filter,

wherein said first adaptation rate of said speech enhancement filter is controlled by a step size β

, wherein said second adaptation rate of said echo cancellation system is controlled by a step size μ

, and wherein β

is much less than μ

, and

wherein said first audio signal is sampled at a sampling frequency F_s, wherein n is the number of samples of the first audio signal accumulated for block processing by said speech enhancement filter, wherein said echo cancellation system includes a plurality of filters and a variable 1/k is the fraction of said plurality of filters that are updated each sampling period, and wherein;

22. The cabin of claim 21, wherein said first adaptation rate is an adaptation rate of a long term noise estimate by said speech enhancement filter, said first adaptation rate is much smaller than said second adaptation rate, and said second adaptation rate is much smaller than a basic filter rate of said speech enhancement filter.

23. The cabin of claim 21, further comprising random noise adding means for adding random noise to the filtered audio signal, said echo cancellation system using the filtered audio signal with the random noise added thereto to identify the third component.

24. The cabin of claim 23, wherein the random noise is a dither signal.

25. The cabin of claim 24, wherein the cabin is movable at a variable velocity and the dither signal is scaled to the velocity.