Patent ID: 6885752
Filing Date: 2005-04-26
Classification: H03G,H04R

Abstract:
1. A multiplicative automatic gain control (AGC) circuit for an apparatus for processing audio signals, said apparatus comprising an input transducer for converting acoustical energy into electrical energy corresponding to said acoustical energy, a plurality of audio bandpass filters coupled to the output of said input transducer, a plurality of said multiplicative AGC circuits comprising noise suppression circuitry, wherein each of said multiplicative AGC circuits is coupled to the output of one of said audio bandpass filters, a first summing junction coupled to the output of said multiplicative AGC circuits, a first amplifier coupled to the output of said first summing junction, and an output transducer for converting electrical energy into acoustical energy, said multiplicative AGC circuit comprising: an absolute value circuit having one input coupled to the output of one of said audio bandpass filters; a first lowpass filter having an input coupled to the output of said absolute value circuit; a logarithmic element having an input coupled to the output of said lowpass filter; a filter element having an input coupled to the output of said logarithmic element; an exponential element having an input coupled to the output of said filter element; a delay element having an input coupled to the input of said absolute value circuit, wherein said delay element compensates for the delay through said filter element; and a multiplier having one input coupled to the output of said exponential element and a second input coupled to the output of said delay element.