Abstract: Taking into consideration of the different situations in which the desktop conference system was applied‚several solutions to the synthesis of stereo signals from mono acoustic signals were theoretically analyzed and compared‚with emphasis on the processing method of the simplified head related transfer function．In this method‚mono acoustic signals were processed and extended to stereo signals．The limitation and the aspects to be improved of the proposed method were also indicated．Moreover‚ by discussing the self-adaptive acoustic echo cancellation and its causes‚several existing echo cancellation structures were analyzed and compared．It is indicated that the structure with a single filter per spatial region is a promising direction of research in echo cancellation‚in which synthesizing stereo signal and setting filter are perfectly combined．

Key words: stereo, head related transfer function, acoustic echo cancellation, desktop conference system