Method of controlling an update algorithm of an adaptive feedback estimation system and a decorrelation unit

Patent metadata

Field	Value
Publication number	US-9269343-B2
Application number	US-201314090847-A
Country	US
Kind code	B2
Filing date	Nov 26, 2013
Priority date	Nov 27, 2012
Publication date	Feb 23, 2016
Grant date	Feb 23, 2016

Abstract

An audio processing device comprises a feedback estimation system for estimating feedback from an output transducer to an input transducer, the feedback estimation system comprising an adaptive filter comprising a variable filter part for filtering an input signal according to variable filter coefficients and an algorithm part comprising an adaptive algorithm for dynamically updating filter coefficients, a control unit for controlling the de-correlation unit and the adaptive algorithm, and a correlation detection unit for determining a) the auto-correlation of a signal of the forward path and providing an AC-value and/or b) the cross-correlation between two different signals of the forward path and providing an XC-value.

First claim

The invention claimed is:

1. An audio processing device comprising at least one input transducer for picking up a sound signal and converting it to at least one electric input signal and at least one output transducer for converting an electric output signal to an output sound, a forward path being defined between the at least one input transducer and the at least one output transducer, the forward path comprising a signal processing unit for processing the at least one electric input signal or a signal derived therefrom and providing a processed output signal and a de-correlation unit for de-correlating the electric output signal and the electric input signal; the audio processing device further comprising an analysis path in parallel to all or a part of the forward path, the analysis path comprising
a feedback estimation system for estimating feedback from the at least one output transducer to the at least one input transducer and providing a corresponding feedback estimation signal, the feedback estimation system comprising an adaptive filter comprising a variable filter part for filtering an input signal according to variable filter coefficients and an algorithm part, the algorithm part comprising an adaptive algorithm for dynamically updating said filter coefficients,
a control unit for controlling said de-correlation unit and said adaptive algorithm, and
a correlation detection unit for determining a) the auto-correlation of a signal of the forward path and providing an AC-value and/or b) the cross-correlation between two different signals of the forward path and providing an XC-value,

wherein the control unit is configured to base or influence its control of said de-correlation unit and said adaptive algorithm on said AC-value and/or said XC-value.

2. An audio processing device according to claim 1 wherein the control unit is configured to apply de-correlation and adaptation rate according to a predefined scheme including different AC- and/or XC-values.

3. An audio processing device according to claim 1 wherein the control unit is configured to decrease the adaptation rate with increasing AC-value and/or XC-value.

4. An audio processing device according to claim 1 wherein the control unit is configured to decrease the adaptation rate with increasing AC-value and/or XC-value, when the AC-value and/or the XC-value is in the range between a first value and a second value, and to decrease the adaptation rate to zero when the AC-value and/or the XC-value is larger than a predefined threshold value larger than or equal to said second value.

5. An audio processing device according to claim 1 comprising a feedback detector configured to indicate whether a given frequency component of a signal of the forward path has its origin in an external signal or in feedback and to provide a control signal to the control unit, and where the control unit is configured to control said de-correlation unit and said adaptive algorithm in dependence of said control signal.

6. An audio processing device according to claim 5 wherein the control unit is configured to increase the adaptation rate and/or to increase the amount of de-correlation when a control signal from the feedback detector indicates that the frequency component in question is due to feedback.

7. An audio processing device according to claim 1 wherein the de-correlation unit is configured to introduce a modulation of a signal of the forward path, in the form of frequency and/or phase and/or amplitude modulation.

8. An audio processing device according to claim 1 wherein the de-correlation unit is configured to introduce a frequency shift in a signal of the forward path.

9. An audio processing device according to claim 1 wherein the control unit is configured to control adaptation rate of the adaptive algorithm and the amount of de-correlation applied to a signal of the forward path at a given point in time in dependence of current characteristics of the signal.

10. An audio processing device according to claim 9 wherein current characteristics of a signal of the forward path comprises its frequency spectrum.

11. An audio processing device according to claim 9 comprising a frequency analyzing unit for analyzing a frequency spectrum of the electric input signal or a signal derived therefrom.

12. An audio processing device according to claim 11 wherein the frequency analyzing unit is configured to determine a fundamental frequency or to determine one or more dominant frequency bands comprising a predefined fraction of the total power of the power spectrum of said electric input signal at a given point in time.

13. An audio processing device according to claim 11 wherein the maximum size of a frequency shift of the de-correlation unit is controlled depending on the analysis of the frequency spectrum relative to a fundamental frequency or to a dominant frequency band of the current frequency spectrum.

14. An audio processing device according to claim 1 wherein pre-determined maximum values or an algorithm for determining such maximum values of de-correlation at different frequencies are stored in a memory of the audio processing device, such values being related to audibility to ensure in-audibility or minimize audibility of the de-correlation.

15. An audio processing device according to claim 14 wherein the control unit is configured to—for a given value of the correlation measure—determine a maximum adaptation rate to be applied to the adaptive algorithm for estimating feedback based on the maximum amount of de-correlation that can be applied to a signal of the forward path at a given point in time without being audible.

16. An audio processing device according to claim 10 comprising a table or an algorithm for providing corresponding values of adaptation rate and amount of de-correlation to be used by the control unit at the occurrence of corresponding values of a de-correlation measure and dominant frequencies of the current frequency spectrum related to signals of the forward path.

17. An audio processing device according to claim 12 wherein the control unit is configured to control the de-correlation unit and/or the adaptive algorithm depending on a bandwidth of a dominant frequency of the current frequency spectrum.

18. An audio processing device according to claim 1 wherein the control unit is configured to provide that the de-correlation unit is inactive AND to allow the adaptive algorithm to adapt the feedback estimate according to a normal scheme, when the AC-values and/or the XC-values are below a predefined first threshold value.

19. An audio processing device according to claim 1 wherein the control unit is configured to provide that the de-correlation unit is active AND to allow the adaptive algorithm to adapt the feedback estimate according to a normal scheme, when the AC-values and/or the XC-values are in a range above a predefined first threshold value and below a second predefined threshold value.

20. An audio processing device according to claim 1 wherein the control unit is configured to provide that the de-correlation unit is inactive AND the adaptive algorithm is inactive when the AC-values and/or the XC-values are larger than a predefined threshold value.

21. An audio processing device according to claim 1 comprising a memory, and being configured to store a number of previous estimates of the feedback path, in order to be able to rely on a previous estimate, if a current estimate is judged to be less optimal.

Assignees

• Oticon As

Inventors

• Munk Steen Michael
• Meng Anders

Classifications

• H04R25/453

  electronically · CPC title

• H04R3/02

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

• G10K11/175 Primary

  using interference effects; Masking sound · CPC title