Patent ID: 6990194

Claim:
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 led 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, said means including: 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 said means controls gain in accordance with the ratio of the averages of the outputs of the acoustic echo canceling circuit and the line echo canceling circuit.