Patent ID: 7664275

Claim:
A method for canceling acoustic feedback in an electronic circuit providing a digital audio signal, the method comprising steps of: producing a digital audio signal at an output of the electronic circuit; preparing the digital audio signal for analysis to detect a feedback signal by transforming the digital audio signal into a frequency domain using a Fast Fourier Transform (FFT) performed on a plurality of buffer sample frames; storing results of the FFT in magnitude and phase arrays in a history buffer; detecting a feedback signal in the digital audio signal by determining a peakness and slopeness of the digital audio signal; detecting a zone of hardly noticeable feedback which represents the zone in a time domain where sound produced by an acoustic feedback is still so quiet that it cannot be heard at all by human listeners; determining a frequency of the feedback signal; and selecting a bandpass filter from among a bank of bandpass filters wherein the selected bandpass filter comprises a response characteristic that attenuates parts of the feedback signal at the frequency of the feedback signal; using the history buffer to store frames of the digital audio signal and calculating a feedback existence probability of the audio signal; wherein the step of preparing the digital audio signal for analysis to detect the feedback signal comprises representing the digital audio signal in a logarithmic domain; wherein the step of determining the frequency of the feedback signal comprises determining the slopeness of the feedback signal at a plurality of points of the logarithmic graph, and wherein determining the slopeness comprises storing at least a part of the digital audio signal in the history buffer, determining a slope at each of the plurality of points of the logarithmic graph and comparing a plurality of slopes in history buffer data, and determining that the feedback signal is present when a substantial deviation from other slopes is detected at a one of the plurality of points; and coupling the bandpass filter selected to an output of the electronic circuit to filter out an acoustic feedback, wherein when a part of the digital audio signal has an amplitude substantially higher than other parts of the digital audio signal, the method comprises recording the frequency of the part of the digital audio signal as a peak to analyze the part of the digital audio signal in the spectral domain over time.