Full duplex speaker-phone providing increased loop stability

Abstract

A full duplex speaker-phone that performs adaptive filtering to provide increased loop stability between users of the speaker-phone. The invention employs a sliding filter that performs adaptive frequency dependent attenuation of the speech signals within a speaker-phone. By detecting the mode of operation of the speaker-phone in real time, the speaker-phone performs adaptive filtering to ensure a high perceptual quality for the users of the speaker-phone. The sliding filtering is performed using a sliding low pass filter (LPF) in certain embodiments of the invention. Perceptually, the speaker-phone does not surrender the appearance of a full duplex speaker-phone from the perspective of the users. In addition, by performing frequency dependent filtering of the speech signals, the speaker-phone offers improved stability in the speaker-phone loop and reduces residual echoes significantly over conventional technology employed in speaker-phones. The sliding filter built in accordance with the present invention is easily implemented, having computational load and memory requirements that are negligible when compared with traditional systems that try to perform filtering in speaker-phones. In certain embodiments of the invention, the attenuation of the speech signals within the speaker-phone are concentrated at higher frequencies.