Patent ID: 7787613

Claim:
An echo canceling circuit comprising: an adaptive filter circuit configured to filter only far-end signals; a threshold estimator configured to iteratively calculate an upper adaptive decision threshold and a lower adaptive decision threshold based on a calculated noise level; and an upper band signal filter configured to pass only near-end upper band signals, wherein near-end speech is declared to be present if an estimated power level of the upper band signals from the upper band signal filter exceeds the upper adaptive decision threshold, wherein the near-end speech is declared to be absent if the estimated power level of the upper band signals from the upper band signal filter falls below the lower adaptive decision threshold for a predetermined number of iterative cycles, wherein the far-end signals are limited in bandwidth by a communication network traversed by the far-end signals to the echo canceling circuit such that the bandwidth of near-end speech available to the echo canceling circuit is greater than the bandwidth of the far-end signals transmitted via the communication system and the upper and lower band signals are present in near end speech but only the lower band signals are present in the far-end signals, and wherein the adaptive filter circuit is adjusted depending on the declaration of the presence of the near-end speech.