Patent ID: 8077858

Claim:
An echo canceler for generating an echo replica signal from a far-end input signal and using the echo replica signal to remove an echo component included in a near-end input signal, thereby obtaining a near-end output signal, the echo canceler comprising: a voice detector for detecting an active state and a silent state of the far-end input signal; a double-talk detector for detecting a single-talk state, a double-talk state, and a silent state from the far-end input signal and the near-end output signal; a normal adaptive filter section that operates while the far-end input signal is active; a silent adaptive filter section for that operates while the far-end input signal is inactive; an adaptive mode controller for controlling operations of the normal adaptive filter section and the silent adaptive filter section on the basis of the active state and the silent state of the far-end input signal as detected by the voice detector; a background noise calculator for calculating an ambient near-end noise power from the near-end output signal when the silent state is detected by the double-talk detector; an echo level detector for detecting an echo power from the near-end output signal when the single-talk state is detected by the double-talk detector; and an averaging controller for calculating a number of vectors to be averaged from an average value of the ambient near-end noise power calculated by the background noise calculator and an average value of the echo power detected by the echo level detector, wherein the silent adaptive filter section includes a data selector for sampling the near-end input signal and the far-end input signal at prescribed intervals for a prescribed duration starting from a time when the voice detector detects a transition from the silent state to the active state to obtain samples, temporarily storing the samples, and generating data vectors from the stored samples, a vector averager for averaging the number of data vectors designated by the averaging controller to generate an averaged far-end input vector and an averaged near-end input vector, an adaptive filter section for convolving the averaged far-end input vector calculated by the vector averager with an internally stored coefficient vector to generate a simulated echo replica signal, subtracting the simulated echo replica signal from the averaged near-end input vector, updating the internally stored coefficient vector, and supplying the updated coefficient vector to the normal adaptive filter section, and an update controller for halting updating of the internally stored coefficient vector in the silent adaptive filter section in the double-talk state, and wherein the averaging controller has a table of ratios of the average ambient near-end noise power to the average echo power and corresponding predetermined values of the number of vectors to be averaged, and obtains the number of vectors to be averaged by referring to the table.