Acoustic echo cancellation with room change detection

Patent metadata

Field	Value
Publication number	US-10790874-B2
Application number	US-201916561436-A
Country	US
Kind code	B2
Filing date	Sep 5, 2019
Priority date	Sep 13, 2018
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

Acoustic echo cancelling includes receiving a source signal and a sink signal; providing a first error signal representative of an echo-free residual signal based on a first set of coefficients based on the source signal and the sink signal, the first error signal forming an output signal of the controller; providing a second error signal based on a second set of coefficients based on the source signal and the sink signal; detecting a room change if the evaluated first second error signal is greater than a sum or product of the evaluated second first error signal and a first threshold; copying one of sets of reference coefficients stored in a memory to the second acoustic echo canceller; and copying the first set of coefficients from the first acoustic echo canceller as a set of reference coefficients into at least one of the second acoustic echo canceller and the memory.

First claim

The invention claimed is:

1. An acoustic echo cancelling controller configured to receive a source signal representative of sound broadcast at a first position in a room and a sink signal representative of sound picked up at a second position in the room, the sound picked up at the second position being transferred from the first position according to a transfer function, the controller comprising:
a first acoustic echo canceller configured to receive the source signal and the sink signal, and to model the transfer function in an adaptive manner based on a first set of coefficients, the first acoustic echo canceller being further configured to provide a first error signal representative of an echo-free residual signal, the first error signal forming an output signal of the controller;
a second acoustic echo canceller configured to receive the source signal and the sink signal, and to model the transfer function in a non-adaptive manner based on a second set of coefficients, the second acoustic echo canceller being further configured to provide a second error signal;
a memory operatively coupled with the first acoustic echo canceller and the second acoustic canceller, the memory being configured to store sets of coefficients from the first acoustic echo canceller as sets of reference coefficient and to provide stored sets of reference coefficients to the second acoustic echo canceller; and
a room change detector operatively coupled with the first acoustic echo canceller and the second acoustic echo canceller, the room change detector being configured to:
evaluate the first error signal and the second error signal, and detect a room change if the evaluated second error signal is greater than a sum or product of the evaluated first error signal and a first threshold,
set, for a predetermined period of time, the second set of coefficients equal to the first set of coefficients if a room change is newly detected, and

copy one of the sets of reference coefficients from the memory to the second acoustic echo canceller and copy the first set of coefficients from the first acoustic echo canceller as another set of reference coefficients into at least one of the second acoustic echo canceller and the memory if a room change is still detected.

2. The controller of claim 1 , further configured to operate in different modes of operation, wherein the room change detector is further configured to copy one of the sets of reference coefficients to at least one of the first acoustic echo canceller and second acoustic echo canceller if the mode of operation is changed.

3. The controller of claim 1 , wherein the room change detector is further configured to detect whether the first acoustic echo canceller is in an adapting or freezing state, and to halt the detection of room changes as long as a freezing state is detected.

4. The controller of claim 1 , wherein:
the first acoustic echo canceller is configured to operate with a controllable adaptation step size, the adaptation step size being controllable based on estimation system distances.

5. The controller of claim 4 , wherein the room change detector is further configured to reset the estimation system distance to a predetermined initialization estimation system distance to adjust an adaptation step size to a first value if a room change is newly detected.

6. The controller of claim 5 , wherein the room change detector is further configured to change the adaptation step size from the first value to a second value that is greater than the first value.

7. The controller of claim 5 , wherein the room change detector is further configured to reset the step size from the second value to the first value if a room change is still detected.

8. The controller of claim 1 , further comprising:
a first smoother configured to evaluate the first error signal by determining the power or level of the first error signal; and
a second smoother configured to evaluate the second error signal by determining the power or level of the second error signal.

9. The controller of claim 1 , wherein the first acoustic echo canceller operates at least partly in the frequency domain based on spectral partitions.

10. The controller of claim 1 , wherein the second acoustic echo canceller operates at least partly in the frequency domain based on spectral partitions.

11. The controller of claim 10 , wherein the second acoustic echo canceller operates based on a single spectral partition.

12. The controller of claim 1 , further configured to receive at least one of a multiplicity of source signals and a multiplicity of sink signals, wherein the first acoustic echo canceller is a multichannel acoustic echo canceller.

13. The controller of claim 1 , further configured to receive at least one of a multiplicity of source signals and a multiplicity of sink signals, wherein the second acoustic echo canceller is a multichannel acoustic echo canceller.

14. The controller of claim 1 , further comprising a third acoustic echo canceller configured to receive the source signal and the sink signal, and to model the transfer function in an adaptive manner based on a third set of coefficients, the third acoustic echo canceller being further configured to provide a third error signal representative of an echo-free residual signal to the room change detector, and to operate with a step size that is greater than a step size of the first acoustic echo canceller.

15. The controller of claim 14 , wherein the room change detector is further configured to set the third set of coefficients equal to the first set of coefficients if the evaluated third error signal is greater than a sum or product of the evaluated first error signal and a second threshold.

16. The controller of claim 14 , wherein the room change detector is further configured to set the first set of coefficients equal to the third set of coefficients if the signal representative of the first error signal is greater than the sum or product of the signal representative of the third error signal and a third threshold value.

17. An acoustic echo cancelling method carried out by a controller having a non-transitory computer readable medium and a processor for executing program code embodied in the non-transitory computer-readable medium, the method comprising the steps of:
receiving a source signal representative of sound broadcast at a first position in a room and a sink signal representative of sound picked up at a second position in the room, the sound picked up at the second position being transferred from the first position according to a transfer function;
first acoustic echo cancelling to model the transfer function in an adaptive manner based on a first set of coefficients to provide a first error signal representative of an echo-free residual signal, the first error signal forming an output signal of the controller;
second acoustic echo cancelling to model the transfer function in a non-adaptive manner based on a second set of coefficients to provide a second error signal;
evaluating the first error signal and the second error signal, and detecting a room change if the evaluated second error signal is greater than a sum or product of the evaluated first error signal and a first threshold;
setting, for a predetermined period of time, the second set of coefficients equal to the first set of coefficients if a room change is newly detected;
copying one of sets of reference coefficients stored in a memory to the second acoustic echo canceller; and
copying the first set of coefficients from the first acoustic echo canceller as a se

Assignees

• Harman Becker Automotive Systems Gmbh

Inventors

• Christoph Markus
• Kandade Rajan Vasudev

Classifications

• H04R3/02 Primary

  for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)} · CPC title

• H04R2430/03

  Synergistic effects of band splitting and sub-band processing · CPC title

• H04M9/082 Primary

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

• G10K11/178

  by electro-acoustically regenerating the original acoustic waves in anti-phase · CPC title

• H04B3/235

  combined with adaptive equaliser · CPC title