Method and device for reducing acoustic feedback
Acoustic feedback in an audio device is reduced or eliminated via a feedback compensator. The feedback compensator disposes of at least one adaptive filter whose adaptation is governed by a step-size parameter μ. A step-size parameter μ of the adaptive filter is set at a high level to eliminate acoustic feedback and the parameter μ is decreased when a critical excitation signal is detected. This way to proceed allows for efficient elimination of feedback whistling while required environment signals are retained.
1. A method of reducing acoustic feedback of an audio device by a feedback compensator, the feedback compensator having at least one adaptive filter, the method comprising the steps of:
setting a step-size parameter p of the adaptive filter at a high level to eliminate acoustic feedback;
using a feedback detector to detect a critical excitation signal being a tonal signal, wherein the tonal signal is a microphone signal which is received by the feedback detector; and
when the critical excitation signal is detected, decreasing the step-size parameter p;
wherein the step-size parameter p controls an adaptation speed of the adaptive filter and wherein the step-size parameter p is set at 0.06 or more to eliminate acoustic feedback.
2. The method according to claim 1 , which comprises controlling the step-size parameter p with a step-size controller.
3. The method according to claim 1 , which comprises processing signals with a signal processing unit prior to the signals being fed to an audio output.
4. The method according to claim 1 , which comprises using a detector for correlated signals to detect the critical excitation signal.
5. The method according to claim 1 , which comprises carrying out a frequency decomposition of excitation signals into frequency subbands, and selectively applying the method to at least one subband.
6. The method according to claim 1 , which comprises employing the method for stabilizing adaption of an adaptive filter.
7. An audio device, comprising:
a feedback compensator for reducing acoustic feedback, said feedback compensator containing at least one adaptive filter controlled with a step-size parameter p;
a feedback detector configured to detect a critical excitation signal being a tonal signal, wherein the tonal signal is a microphone signal which is received by said feedback detector; and
a step-size controller configured for setting the step-size parameter p of said adaptive filter at a relatively high level to eliminate acoustic feedback;
said step-size controller configured for decreasing the step-size parameter p when said feedback detector detects the critical excitation signal;
wherein the critical signal is a tonal signal; and
wherein the step-size parameter p controls an adaptation speed of said adaptive filter and wherein the step-size parameter p is set at 0.06 or more to eliminate acoustic feedback.
8. The audio device according to claim 7 , further comprising a step-size controller configured for controlling the step-size parameter p.
9. The audio device according to claim 7 , further comprising a signal processing unit for processing signals before the signals are fed to an audio output.
10. The audio device according to claim 7 , further comprising a detector for correlated signals to detect the critical excitation signal.
11. The audio device according to claim 7 , configured for operation to perform a frequency decomposition of excitation signals into subbands.