Dynamic balance control for telephone
First Claim
1. In a telephone including an audio frequency circuit having a transmit channel and a receive channel, an acoustic echo canceling circuit, a line echo canceling circuit, and a noise reduction circuit coupled to the channels, and wherein each channel includes a filter bank for dividing the channel into a plurality of sub-bands, the improvement comprising:
- a plurality of voice activity detectors coupled one to each sub-band filter, wherein each voice activity detector produces a signal indicative of the energy content of an input signal to the detector;
a plurality of variable gain amplifiers coupled one each to a voice activity detector in the receive channel;
a plurality of comparators coupled one each to a pair of voice activity detectors, wherein each pair includes a voice activity detector from the transmit channel and the variable gain amplifier from the corresponding voice activity detector coupled to the receive channel;
means for controlling the gain of said variable gain amplifiers to provide a predetermined balance between the channels.
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Accused Products
Abstract
A telephone includes a transmit channel and a receive channel, each including a bank of sub-band filters having a VAD coupled one to each sub-band filter. Each VAD measures the spectral energy in a sub-band, compares the spectral energy to a first threshold, and produces an output signal representative of whether or not the first threshold is exceeded. The voice activity detector also includes a threshold circuit for calculating a dynamically adjustable noise threshold based upon averaged measured spectral energy. A wide band or system VAD monitors echo canceling circuitry to detect voice activity and double talk. A dynamic balance control circuit maintains the transmit and receive channels in a predetermined energy ratio during double talk.
17 Citations
14 Claims
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1. In a telephone including an audio frequency circuit having a transmit channel and a receive channel, an acoustic echo canceling circuit, a line echo canceling circuit, and a noise reduction circuit coupled to the channels, and wherein each channel includes a filter bank for dividing the channel into a plurality of sub-bands, the improvement comprising:
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a plurality of voice activity detectors coupled one to each sub-band filter, wherein each voice activity detector produces a signal indicative of the energy content of an input signal to the detector;
a plurality of variable gain amplifiers coupled one each to a voice activity detector in the receive channel;
a plurality of comparators coupled one each to a pair of voice activity detectors, wherein each pair includes a voice activity detector from the transmit channel and the variable gain amplifier from the corresponding voice activity detector coupled to the receive channel;
means for controlling the gain of said variable gain amplifiers to provide a predetermined balance between the channels. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a telephone including an audio frequency circuit having a transmit channel having variable gain and a receive channel having variable gain, an acoustic echo canceling circuit, and a line echo canceling circuit, the improvement comprising:
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a first averaging circuit coupled to the output of the acoustic echo canceller;
a second averaging circuit coupled to the output of the line echo canceller; and
a ratio detector coupled to the first averaging circuit and the second averaging circuit;
wherein the output of the ratio detector controls gain in each channel. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification