Acoustic echo canceler using an accelerometer
A system includes a loudspeaker, a microphone, an echo canceling circuit, and an accelerometer coupled to the loudspeaker for providing a reference signal, a(n), to the echo canceling circuit. Preferably, the accelerometer is attached to the loudspeaker. A speaker signal, x(n), is used to drive the loudspeaker and the system also includes a switch for coupling either a(n) or x(n) to the echo canceling circuit, depending upon the volume or loudness of the sounds involved.
1. A system for reducing nonlinear echoes in an acoustic signal, the system comprising in combination:
a) a loudspeaker for reproducing audio signals, the loudspeaker occasionally generating non-linear distortion signals;
b) a signal processor having an output for providing an output audio signal to be reproduced by the loudspeaker, the signal processor also having a first input and a second input;
c) a microphone for detecting speech by a user, the microphone being coupled to the first input of the signal processor;
d) an accelerometer physically coupled to the loudspeaker for generating signals indicative of movement by the loudspeaker corresponding to non-linear distortion signals, the accelerometer being coupled to the second input of the signal processor;
e) the signal processor including an adaptive filter for subtracting non-linear distortion signals presented by the accelerometer to the second input of the signal processor from audio signals presented by the microphone to the first input of the signal processor before providing the output audio signal to the loudspeaker.
2. The system for reducing nonlinear echoes as recited in claim 1 wherein the first adaptive filter generates a digital output signal, and wherein said signal processor includes a digital-to-analog converter for providing an analog signal to the loudspeaker.
3. The system for reducing nonlinear echoes as recited in claim 2 further including a switch coupled to the second input of the signal processor, the switch having at least a first state and a second state, the first state of the switch coupling the accelerometer to the second input of the signal processor for supplying non-linear distortion signals, and the second state of the switch coupling the digital output signal of the adaptive filter to the second input of the signal processor.
4. The system for reducing nonlinear echoes as recited in claim 3 wherein the adaptive filter used to reduce nonlinear echoes is also used to reduce linear echo signals.