Patent ID: 6055318
Filing Date: 2000-04-25
Classification: H03H

Abstract:
A method for dynamic noise reduction of an audio signal in an audio reproduction system comprising the steps of:lowpass filtering said audio signal in an adaptive lowpass filter having a plurality of filter coefficients to control an upper cutoff frequency of said lowpass filter;time averaging an input audio signal at an input to said adaptive lowpass filter to obtain an input average;time averaging an output audio signal at an output from said adaptive lowpass filter to obtain an output average;multiplying one of said averages by a percentage constant;forming a difference between said multiplied average and the other one of said averages to obtain an error using a time constant;adapting said filter coefficients to cancel said error;comparing said input average with a low modulation threshold; andinhibiting at least a portion of said adapting step if said input average is below said low modulation threshold.