说明：  　阐述回声消除技术原理,介绍自适应回声消除器基本结构,分析两类消除回声的基本算法,并提出基于两类算法的几种改进型算法,为提高IP电话的话音质量提供一定的参考。
(　The element of the echo cancellation and the configuration of the adaptive echo canceller is first in troduced in this paper. It also analyzed two kinds of basical go rithms on echo cancellation , then based on which a few improving algorithms were provided . These can provide reference for improving speech quality on IP.)