AUDIO SYSTEM WITH FEEDBACK CANCELLATION

• US 20110103613A1
• Filed: 04/08/2009
• Published: 05/05/2011
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: GN Resound A/S (GN Store Nord A/S)
• Original Assignee: GN Resound A/S (GN Store Nord A/S)
• Inventors: Van Der Werf, Erik Cornelis Diederik, Bisgaard, Nikolai
• Granted Patent: US 9,179,223 B2
• Time in Patent Office: Days
• US Class Current: 381/93
• CPC Class Codes: H04R 25/453 electronically
• CPC Class Codes: H04R 3/02 for preventing acoustic reaction , i.e. acoustic oscillatory feedback specially adapted for hearing aids H04R25/453

Abstract

An audio system includes a signal processor for processing an audio signal, and a feedback suppressor circuit configured for modelling a feedback signal path of the audio system by provision of a feedback compensation signal based on sets of feedback model parameters for the feedback signal path that are stored in a repository.

Claims

1. An audio system comprising:

a signal processor for processing an audio signal, and

a feedback suppressor circuit configured for modelling a feedback signal path of the audio system by provision of a feedback compensation signal based on sets of feedback model parameters for the feedback signal path that are stored in a repository.

2. The audio system according to claim 1, further comprising a first subtractor for subtracting the feedback compensation signal from the audio signal to form a compensated audio signal supplied to the signal processor.

3. The audio system according to claim 1, further comprising an environment detector for detection of a sound environment of the audio system, and wherein the feedback suppressor circuit is further configured for determining an additional set of feedback model parameters based on the sound environment detection and the sets of feedback model parameters stored in the repository for modelling the feedback signal path corresponding to the detected sound environment.

4. The audio system according to claim 1, wherein the feedback suppressor circuit is further configured for clustering the sets of the feedback model parameters to obtain a plurality of clusters.

5. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for selecting one of the clusters corresponding to a detected sound environment for modelling of the feedback signal path.

6. The audio system according to claim 4, wherein the feedback suppressor circuit is configured for modelling the feedback signal path based on feedback model parameters of a centre of the selected cluster.

7. The audio system according to claim 1, wherein the feedback suppressor circuit comprises an adaptive filter for modelling the feedback path, and wherein the sets of the feedback model parameters stored in the repository comprise filter coefficients of the adaptive filter.

8. The audio system according to claim 7, further comprising a switch that is configured for switching an input to the signal processor between an output of a first subtractor and an output of a second subtractor for subtracting an output signal of the adaptive filter from the audio signal.

9. The audio system according to claim 1, wherein the feedback suppressor circuit comprises a digital filter with filter coefficients obtained using one or more of the sets of feedback model parameters stored in the repository.

10. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for merging two of the clusters when their mutual similarity distance is less than a threshold value.

11. The audio system according to claim 10, wherein the threshold value is a function of a similarity distance between current feedback model parameters determined by the feedback suppressor circuit and their nearest cluster centre.

12. The audio system according to claim 10, wherein the threshold value is a function of a dissimilarity between two of the clusters that are most similar.

13. The audio system according to claim 10, wherein the threshold value is a function of deviations within the clusters.

14. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for deleting one of the clusters when its membership count is below a threshold value.

15. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for creating a new cluster when an similarity distance to a nearest cluster is larger than a threshold value.

16. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for splitting one of the clusters when a similarity distance within the one of the clusters is larger than a threshold value.

17. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured to maintain one of the clusters unchanged when it has been used effectively for a certain period of time.

18. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for identifying a smallest cluster with a lowest membership count, and replacing that cluster with current feedback model parameters determined by the feedback suppressor circuit, provided that the lowest membership count is below a threshold value and that a similarity distance from the smallest cluster to its nearest cluster is larger than a similarity threshold value.

19. The audio system according to claim 7, wherein the feedback suppressor circuit is further configured for constrained updating the filter coefficients of the adaptive filter.

20. The audio system according to claim 7, wherein the feedback suppressor circuit is configured for updating the filter coefficients of the adaptive filter by applying a de-correlation.

21. The audio system according to claim 20, wherein the feedback suppressor circuit is configured to apply the de-correlation to an error signal.

22. The audio system according to claim 20, further comprising a fixed filter for the de-correlation.

23. The audio system according to claim 1, wherein at least one of the sets of the feedback model parameters is predetermined.

24. The audio system according to claim 1, wherein adaptive non-linear de-correlation is applied in the signal path.

25. The audio system according to claim 24, wherein the adaptive non-linear de-correlation is applied depending on a selected cluster or feedback model.

26. The audio system according to claim 1, wherein a gain reduction is applied in the signal path depending on a selected cluster or feedback model.

27. The audio system according to claim 4, wherein the feedback suppressor circuit is further configured for maintaining a statistical model of the feedback path in a form of a Gaussian mixture model.

28. The audio system according to claims 27, wherein the feedback suppressor circuit is further configured to share statistical information between two of the clusters.

29. The audio system according to claim 1, wherein the feedback suppressor circuit is further configured for maintaining a statistical model of an external signal to distinguish correlations between an output of the audio system and an input caused by feedback from correlations already present in the external signal.

30. The audio system according to claim 1, wherein the feedback suppressor circuit is further configured for maintaining clustering models for the feedback path and a clustering model of an external signal.

31. The audio system according to claim 4, wherein the feedback suppressor circuit is configured to select one of the clusters, and use the selected cluster to detect speech.

32. The audio system according to claim 1, wherein the feedback suppressor circuit is further configured to operate on multiple input signals independently.

33. The audio system according to claim 32, wherein the feedback suppressor circuit is further configured to share information between the multiple input signals.

34. The audio system according to claim 32, wherein the feedback suppressor circuit is further configured to use a shared signal model for the input signals.

35. The audio system according to claim 32, wherein the feedback suppressor circuit is further configured with clustering models that combine feedback paths of all or some of the multiple input signals.

36. The audio system according to claim 1, wherein the feedback suppressor circuit takes into account higher order statistics to characterize receiver, amplifier, and/or microphone non-linearities in the feedback path.

37. The audio system according to claim 4, further comprising a log for recording the clusters and selected feedback model statistics.

38. The audio system according to claim 37, wherein the log is also for recording performance of the feedback suppressor circuit.

39. The audio system according to claim 37, where the log is also for recording encountered signal model statistics.

40. The audio system according to claim 1, wherein a selected feedback model is used by the audio system to detect a presence of a nearby reflection.

41. The audio system of claim 40, wherein the reflection comprises a phone.

42. The audio system according to claim 1, wherein a current signal model is used by the system to detect a use of a phone.

43. The audio system according to claim 4, wherein the feedback suppressor circuit is configured to select one of the clusters, and wherein the selected cluster is used to detect when the audio system is put in, taken out, or placed incorrectly to a ear or a user.

44. The audio system according to claim 1, further comprising the repository.