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An arrangement for generating an electrical audio signal in response to a sound signal applied to a microphone in a reverberating room removes the reverberations with an adaptive filter. The filter learns or adapts so as to cancel the room echoes by receiving both the audio signal affected by reverb

An arrangement for generating an electrical audio signal in response to a sound signal applied to a microphone in a reverberating room removes the reverberations with an adaptive filter. The filter learns or adapts so as to cancel the room echoes by receiving both the audio signal affected by reverberation and a clean audio signal from a highly directional local-acting microphone placed near the source of the sound. The signal to be filtered is applied to a transversal filter including a tapped delay line having variable taps or multipliers to produce incrementally delayed multiplied samples. The multiplied samples are summed, and the sum signal is subtracted from the clean signal to produce a difference signal. A m

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A method for reducing the effect of room resonances on the quality of sound transmitted over a speakerphone including a loudspeaker-microphone pair and a handset transmitter-receiver pair, comprising the steps of: speaking into said transmitter of said handset at a location in said room so that a cl

A method for reducing the effect of room resonances on the quality of sound transmitted over a speakerphone including a loudspeaker-microphone pair and a handset transmitter-receiver pair, comprising the steps of: speaking into said transmitter of said handset at a location in said room so that a clean audio signal is generated by said transmitter which is unaffected by said room resonances, and a corresponding audio signal is generated by said microphone which is affected by said room resonances; delaying said corresponding audio signal to produce a plurality of incrementally delayed samples of said corresponding audio signal; multiplying each of said incrementally delayed samples of said corresponding audio signal by one of a plurality of multipliers to produce a plurality of multiplied signals; summing together said multiplied signals to produce a sum signal; subtracting said sum signal from said clean audio signal to produce a difference signal; adjusting each of said plurality of multipliers so as to reduce said difference signal towards zero, whereby said sum signal approximates said clean signal; fixing the values of each of said plurality of multipliers to produce fixed multipliers which multiply said incrementally delayed samples of said corresponding audio signal, whereby said sum signals is said corresponding audio signal corrected for said room resonances; ceasing speech into said transmitter of said handset after said fixing step; speaking towards said microphone after said ceasing step; and utilizing said sum signal as the output of said speakerphone.