Ambient noise suppression circuit
First Claim
1. An ambient noise suppression circuit for a hands-free voice communication terminal comprising a microphone, means for positioning the microphone for hands-free operation, a gain control amplifier receiving a signal from the microphone, and a peak-hold circuit that comprises:
- (i) a band-pass amplifier that amplifies a specified frequency range of audio output signals of said microphone,(ii) a peak detection circuit that produces signals related to the peak amplitude of output signals of the said band-pass amplifier, and(iii) a holding circuit that holds the amplitude of the produced signals of said peak detection circuit without significant reduction for a specified period of time and produces a peak-hold output signal; and
wherein the peak-hold output signal is applied solely and directly to control gain of said gain control amplifier in direct relation to the peak-hold output signal.
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Accused Products
Abstract
An ambient noise suppression electrical circuit to be used with a voice communication terminal comprising a gain control amplifier, whose input is a microphone, and a peak-hold circuit that includes a band-pass amplifier that amplifies a specified frequency range of the output signals of the microphone, a peak detection circuit that produces signals in proportion to the peak level of the output signals of the band-pass amplifier, and a holding circuit that controls reduction of output signals of the peak detection circuit for a specified period of time. The output signal from the peak-hold circuit controls the gain of the gain control amplifier. When a microphone is located far from a mouth and is used under high ambient noise, the present invention makes it possible for the microphone to perform as if it is a microphone which is located in a quality telephone handset that cuts off ambient noise.
28 Citations
7 Claims
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1. An ambient noise suppression circuit for a hands-free voice communication terminal comprising a microphone, means for positioning the microphone for hands-free operation, a gain control amplifier receiving a signal from the microphone, and a peak-hold circuit that comprises:
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(i) a band-pass amplifier that amplifies a specified frequency range of audio output signals of said microphone, (ii) a peak detection circuit that produces signals related to the peak amplitude of output signals of the said band-pass amplifier, and (iii) a holding circuit that holds the amplitude of the produced signals of said peak detection circuit without significant reduction for a specified period of time and produces a peak-hold output signal; and wherein the peak-hold output signal is applied solely and directly to control gain of said gain control amplifier in direct relation to the peak-hold output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification