Process and apparatus for eliminating loudspeaker interference from microphone signals

A filter system comprising:

• a stereo sampling unit to sample a microphone signal and a loudspeaker signal;
• a computation unit for generating a transfer function between the microphone signal and the loudspeaker signal;
• and
• a filter unit;
• wherein said stereo sampling unit samples the microphone signal to generate a microphone signal sample x(t) in the time domain;
• and
• said stereo sampling unit samples said loudspeaker signal to generate a loudspeaker signal sample z(t) in the time domain;
• and
• said computation unit comprising:
• a Fourier transform unit;
• said Fourier transform unit to compute a microphone spectrum X(f,T) and a loudspeaker spectrum Z(f,T),
• multiplying, smoothing and division layers;
• said multiplying, smoothing and division layers for processing said spectra X(f,T) and Z(f,T),
• a convolution layer;
• said convolution layer to convolve inputs to produce a transfer function H(f,T);
• and
• a time delay unit to determine the signal propagation delay d between said microphone signal and said loudspeaker signal,
• wherein said computation unit uses said microphone signal sample x(t), said loudspeaker signal sample z(t), said microphone spectrum X(f,T) and said loudpseaker spectrum Z(f,T) to generate said transfer function H(f,T), and
• said filter unit uses said microphone signal sample x(t), said loudspeaker signal sample z(t), and said transfer function H(f,T) to generate an interference free signal, y(t).