Research On Speech Signal Dereverberation

In relatively enclosed space such as conference room,gymnasium etc,if the distance of sources is far away from the microphone,strong reverberation will have negative impact on the quality of speech signal,furthermore,this resultsin speech confusing,difficult recognization.Therefore,speech signal dereverberation becomes very important for communication,hearing-aid system telconference system,and so on.The main work includes these aspects:firstly,introduced the speech signal theory knowledge is introduced,including the mathematical model of the speech signal,short-term analysis,processing methods,linear prediction analysis and short-term synthesis;secondly,the principle of reverberation is introduced,including reverberation time,mathematic model,characteristics and various reverberation method;thirdly,reverberation technology application fields and development prospects are summaried;fourthly,the evaluation methods of speech dereverberation are introduced,which includes three subjective evaluation methods and two objective evaluation methods.Fifthly,the basic theory of homomorphic processing as well as the concept of complex cepstrum is introduced,including its properties and calculation method.Lastly,complex cepstrum domain filter is designed for speech reverberation.Due to the disadvantages of the single channel dereverberation technology,microphone array dereverberation methods are also studied.Therefore,this paper continue to study the microphone array dereverberation.Studied the basic concept of microphone arrays,analyzed the awareness,the human ear model.The difference of microphone array between the far field model and the near field model are introduced.The various speech enhancement methods are introduced,including fixed beamforming method,the adaptive beamforming method,the rear filter method and subspace method,etc..And analyzed the time delay estimation of fixed beamforming method.Fixed beamforming method combined with complex cepstrum dereverberation theory,and made simulation research.compared complex cepstrum with fixed beamforming method,found that the method has obtained better to reverberation effect.