Multi-channel adaptive speech signal processing system with noise reduction

A method for reducing noise comprising:

• receiving multiple microphone input signals;
• applying a time delay compensation to the microphone input signals, thereby generating time delay compensated microphone output signals;
• generating noise reference output signals based on the time delay compensated microphone output signals;
• repeatedly updating weights in an adaptive beamformer responsive to temporal changes in the microphone input signals;
• beamforming the time delay compensated microphone output signals into a beamformed signal based on the weights;
• generating a noise reference signal based on the noise reference output signal;
• and
• subtracting the noise reference signal from the beamformed signal.

A product comprising:

• a machine readable medium;
• and
• instructions encoded on the medium which cause a processor in a noise reduction signal processing system to perform a method comprising:
• receiving multiple microphone input signals;
• applying a time delay compensation to the microphone input signals, thereby generating time delay compensated microphone output signals;
• generating noise reference output signals based on the time delay compensated microphone output signals;
• repeatedly updating weights in an adaptive beamformer;
• beamforming the time delay compensated microphone output signals into a beamformed signal based on the weights;
• generating a noise reference signal based on the noise reference signal outputs;
• and
• subtracting the noise reference signal from the beamformed signal.

A noise reduction signal processing system comprising:

• multiple microphone signal inputs comprising first directional microphone signal inputs and second directional microphone signal inputs from microphones pointing in different directions;
• time delay compensation logic coupled to the microphone signal inputs and comprising time delay compensated microphone signal outputs;
• adaptive self-calibration logic coupled to the time delay compensation logic, the adaptive self-calibration logic operable to match at least one of phase and amplitude of time delay compensated microphone output signals on the time delay compensated microphone signal outputs;
• an adaptive blocking matrix coupled to the adaptive self-calibration logic and comprising noise reference signal outputs;
• an adaptive beamformer coupled to the adaptive self-calibration logic which determines a beamformed signal according to:
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• where ‘Yw’ is the beamformed signal, ‘n’ is a frequency bin index, ‘k’ is a time index, there are ‘M’ time delay compensated microphone output signals, ‘Am(n)’ is a repeatedly adapted real-valued weight, and ‘XT,m’ is a time delay compensated microphone output signal;
• adaptive noise cancellation logic coupled to the noise reference signal outputs and the beamformed signal output and comprising an adaptive noise cancellation output, the adaptive noise cancellation logic operable to generate a noise reference signal on the adaptive noise cancellation output;
• and
• summing logic for removing noise in the beamformed signal using the noise reference signal.