Design Of Adaptive Acoustic Echo Cancellation Based On DSP Systems

Hands-free speech communication is indispensable in audio and video conference systems,hot-line telephones and videophones, digital ISDN network, mobile radio terminals etc,people demand higher and higher speech quality in communication. However,it is not always easy to implement acoustic equipments for communication system with satisfactory speech quality.Because echo which exist in many communication circumstance can badly influence audio definition.The most important requirement is to protect against howling and echo,due to acoustic feeback from loudspeaker to microphone,and to ensure a sufficient listening level.So acoustic echo cancellation(AEC) technique has become a hot issue of competition in the famous communication company all over the world.The fundament of AEC is cancelling the echo by employing an adaptive filter to identify and simulate the real echo paths.What makes the capability of an adaptive algorithm applied in AEC very demanding is the highly nonstationary nature of the involved signals and systems.With increasingly more signal processing power available of Digital Signal Processors(DSP) in recent years,the applications of an adaptive filter parallel to the loudspeaker- microphone system in real time become economically feasible.Firstly,this paper discusses about some algorithms of adaptive filtering such as LMS and NLMS.The convergent speed and steady-state error are affected by the fixed step size and can't be improved simultaneously in classical LMS algorithm. Improve on an algorithm of LMS through a function relationship between μ and n.With computer simulation result confirm that the new algorithm is better than classical LMS and NLMS,besides good practical performance.On the basis of theoretical investigation and simulation,an acoustic echo cancellor has been made using TMS320VC5402(fix-point DSP).This algorithm has been implemented on this cancellor in the real-time processing.lt has been proved that the new algorighm can obtain a satisfied echo cancellation result and improve the quality of voice communication.