Echo cancellation

Patent metadata

Field	Value
Publication number	US-9509854-B2
Application number	US-57691505-A
Country	US
Kind code	B2
Filing date	Oct 13, 2005
Priority date	Oct 13, 2004
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

An echo cancellation device including a first adaptive filter for producing a first echo cancellation signal, a second adaptive filter for producing a second echo cancellation signal, and a post-processor for suppressing any remaining echo. The first adaptive filter and the second adaptive filter are designed for canceling a first part of the echo impulse response and a second part of the echo impulse response respectively. The device may be utilized in a mobile telephone.

First claim

The invention claimed is:

1. An echo cancellation device for canceling an echo in a microphone signal in response to a far-end signal, the device comprising:
a first section including a first adaptive filter for receiving the far-end signal to produce a first echo cancellation signal for a first part of an impulse response only from t=0 to t=T corresponding with a direct part of the impulse response, and a first combination unit for receiving the first echo cancellation signal and the microphone signal to produce a first residual signal;
a second section including a second adaptive filter for receiving a delayed far-end signal to produce a second echo cancellation signal for a second part of the impulse response only from t=T corresponding with a diffuse part of the impulse response such that the second part of the impulse response is a different part than the first part of the impulse response, and a second combination unit for receiving the second echo cancellation signal and the first residual signal to produce a second residual signal;
a delay unit for providing a delay of the far-end signal, the delay causes the first echo cancellation signal to substantially cancel the impulse response during a first plurality of samples of the signal taken during t=0 to t=T and the second echo cancellation signal to substantially cancel the impulse response during the second plurality of samples of the signal taken after t=T; and
a post-processor for receiving the first and second echo cancellation signals, the second residual signal, and the microphone signal to produce a processed residual signal as a weighted spectral subtraction of the first and second echo cancellation signals substantially excluding any remaining echoes.

2. The device according to claim 1 , wherein the post-processor directly receives the microphone signal.

3. The device according to claim 1 , further comprising: at least one filter update unit included in each of the first and second sections.

4. The device according to claim 1 , wherein the delay substantially corresponding to a filter length of the first adaptive filter.

5. The device according to claim 1 , further comprising a tail estimation unit for estimating an echo tail of the microphone signal and providing the estimated echo tail to the post-processor.

6. The device according to claim 1 , wherein a combined echo cancellation signal is a combination of the first and the second echo cancellation signals.

7. The device according to claim 1 , wherein the spectral subtraction involves over-subtraction factors.

8. The device according to claim 1 , included in an audio system.

9. The device according to claim 1 , included in a mobile telephone device.

10. The device according to claim 1 , wherein the first and second plurality of samples are contiguous sets of samples.

11. The device according to claim 1 , wherein during the first plurality of samples, the energy decay curve of the impulse response includes a spike increase and the first plurality of samples ends when the energy decay curves begins a substantially linear decay.

12. The device according to claim 1 , wherein during the second plurality of samples, the energy decay curve of the impulse response is substantially linearly decaying.

13. A method of canceling an echo in a microphone signal in response to a far-end signal, the method comprising acts of:
filtering the far-end signal to produce a first echo cancellation signal for a first part of an impulse response only from t=0 to t=T corresponding with a direct part of an impulse response;
filtering a delayed far-end signal to produce a second echo cancellation signal for a second part of the impulse response only from t=T corresponding with a diffuse part of the impulse response such that the second part of the impulse response is a different part than the first part of the impulse response;
combining the first echo cancellation signal with the microphone signal to produce a first residual signal, and second echo cancellation signal with the first residual signal to produce a second residual signal;
providing a delay of the far-end signal, the delay causes the first echo cancellation signal to substantially cancel the impulse response during a first plurality of samples of the signal taken during t=0 to t=T and the second echo cancellation signal to substantially cancel the impulse response during the second plurality of samples of the signal taken after t=T; and
processing the first and second echo cancellation signals, the second residual signal, and the microphone signal to produce a processed residual signal as a weighted spectral subtraction of the first and second echo cancellation signals substantially excluding any remaining echoes.

14. The method according to claim 13 , wherein the processing involves spectral subtraction.

15. The method according to claim 13 , further comprising an act of estimating a tail of the microphone signal, wherein the processing involves utilizing the estimated signal tail.

16. The method according to claim 13 , embodied on a computer readable non-transitory medium.

17. The method according to claim 13 , wherein the act of processing comprises an act of processing the first and second plurality of samples as contiguous sets of samples.

18. The method according to claim 13 , wherein during the first plurality of samples, the energy decay curve of the impulse response includes a spike increase and the first plurality of samples ends when the energy decay curves begins a substantially linear decay.

19. The method according to claim 13 , wherein during the second plurality of samples, the energy decay curve of the impulse response is substantially linearly decaying.

Assignees

• Merks Ivo Leon Diane Marie
• Janse Cornelis Pieter
• Derkx Rene Martinus Maria
• Koninklijke Philips Nv

Inventors

• Merks Ivo Leon Diane Marie
• Janse Cornelis Pieter
• Derkx Rene Martinus Maria

Classifications

• G10L2021/02082

  the noise being echo, reverberation of the speech · CPC title

• H04B3/23

  using a replica of transmitted signal in the time domain, e.g. echo cancellers · CPC title

• H04R3/002

  Damping circuit arrangements for transducers, e.g. motional feedback circuits · CPC title

• H04M9/082 Primary

  using echo cancellers (echo cancellers per se H04B3/23) · CPC title

• G10L21/0208 Primary

  Noise filtering · CPC title