Audio feedback reduction utilizing adaptive filters and nonlinear processing
View Patent ↗Systems and methods for holistically modelling audio feedback and removing the entire feedback signal corresponding thereto. The systems can operate at a much larger loop-gain (and hence with a much higher loudspeaker volume), than those conventional systems which seek to remove singing frequencies with PEQs. The systems are an improvement over traditional audio feedback elimination systems which attempt to reduce the effect of the audio feedback by simply scaling down the audio volume of the signal frequencies that are prone to howling, and those feedback elimination systems which simply employ adaptive notch filtering to detect and “notch” the so-called “singing” or “howling” frequencies as they occur in real-time. Such devices may typically have several knobs and buttons needing tuning, for example: the number of adaptive parametric equalizers (PEQs) versus fixed PEQs; attack and decay timers; and/or PEQ bandwidth. The systems set forth herein obviate the need for tuning knobs or buttons, making set up easy.
1. A system for eliminating audio acoustic feedback, comprising:
one or more speakers configured to produce an output audio signal;
one or more microphones configured to capture an input audio signal, wherein the input audio signal may comprise at least a portion of the output audio signal;
an audio mixer operatively coupled to the one or more microphones;
an audio amplifier operatively coupled to the one or more speakers; and
a feedback elimination system operatively coupled between the audio mixer and the audio amplifier, the feedback elimination system configured to:
analyze, using a dual-subband data structure with a first crossover frequency, the input audio signal, wherein each subband comprises two or more adaptive filter taps;
estimate an echo return loss in the input audio signal;
detect a double talk condition in the input audio signal;
suppress echo in the input audio signal based, at least in part, on the analysis of the input audio signal, the estimated echo return loss, and the detected double talk condition; and
synthesize the output audio signal based, at least in part, on the input audio signal with suppressed echo.
2. The system of claim 1 , wherein each adaptive filter tap is smoothed over time.
3. The system of claim 1 , wherein the first crossover frequency is 1000 Hz.
4. The system of claim 1 , wherein the dual-band data structure uses a 128-subband decomposition and a 256-subband decomposition operation.
5. The system of claim 1 , wherein synthesizing the output audio signal based, at least in part, on the input audio signal with suppressed echo, comprises overlap-adding the frequency range from zero Hz to the crossover with the frequency range greater than the crossover frequency.
6. The system of claim 1 , wherein the two or more adaptive filter taps comprise a transient filter tap and a slow filter tap.
7. A non-transitory computer readable storage medium storing instructions for eliminating audio acoustic feedback, the instructions executable by at least one processor and comprising instructions to:
receive an input audio signal from one or more microphones, the input audio signal comprising at least a portion of a first output audio signal produced by one or more speakers;
analyze, using a dual-subband data structure with a first crossover frequency, the input audio signal, wherein each subband comprises two or more adaptive filter taps;
estimate an echo return loss in the input audio signal;
detect a double talk condition in the input audio signal;
suppress echo in the input audio signal based, at least in part, on the analysis of the input audio signal, the estimated echo return loss, and the detected double talk condition; and
synthesize a second output audio signal based, at least in part, on the input audio signal with suppressed echo.
8. The non-transitory computer readable storage medium of claim 7 , wherein each adaptive filter tap is smoothed over time.
9. The non-transitory computer readable storage medium of claim 7 , wherein the first crossover frequency is 1000 Hz.
10. The non-transitory computer readable storage medium of claim 7 , wherein the dual-band data structure uses a 128-subband decomposition and a 256-subband decomposition operation.
11. The non-transitory computer readable storage medium of claim 7 , wherein the instructions to synthesize the output audio signal based, at least in part, on the input audio signal with suppressed echo, comprises overlap-adding the frequency range from zero Hz to the crossover with the frequency range greater than the crossover frequency.
12. The non-transitory computer readable storage medium of claim 7 , wherein the two or more adaptive filter taps comprise a transient filter tap and a slow filter tap.
13. The non-transitory computer readable storage medium of claim 7 , wherein the instructions further comprise instructions to transmit the second output audio signal to the one or more speakers.