Study On Methods Of Microphone Array Based Sound Source Localization And Speech Enhancement

In many speech communication systems, such as hands-free telephone and video-conference, the speech signal received by a microphone is often corrupted by the rever-berations and background noises. It not only a?ects the intelligibility of speech signals,but also degrades the overall performance of speech processing systems. Therefore,it is necessary to develop speech enhancement methods to suppress the interferencenoises. In diverse acoustical environments, speech enhancement from a single mi-crophone fails to meet the requirements. While, an alternative solution, referred toas microphone array processing techniques, can obtain a significant noise reduction bycapturing the location of a sound source and implementing the spatial filtering on noisysignals. Herein, this dissertation focuses on microphone array based sound source lo-calization and speech enhancement methods, and the contributions are as follows.(1) Summarized the di?erent kinds of time delay estimation (TDE) techniques.Specifically, the most popular TDE methods are studied on tracking ability ofstationary and moving sources, robustness under di?erent reverberation levelsand signal-to-noise ratios (SNR), as well as the computational complexity. Basedon simulation results, this dissertation presents the advantages and disadvantagesof these algorithms and their applications.(2) Proposed a dual-microphone based source localization method in 2D space. Bycombining the information of time delay and energy attenuation of the receivedsignals, the proposed method reduces the number of microphones for localiza-tion to 2. Compared with 3 microphones required in the conventional two-steplocalization methods, this work cuts o? the device cost. Besides, the closed formsolution obtained in this dissertation facilitates the algorithm's implementationand procession. Furthermore, under the assumption of Gaussian measurementerror, the Cramer-Rao lower bound of the estimated position's variance is derivedfor the proposed localization model, and the impacts of di?erent parameters on localizing accuracy are also analyzed.(3) Proposed a high resolution direction of arrival (DOA) estimation method basedon searching space pre-estimation. This work utilizes the TDE result to obtaina candidate searching space for the high resolution DOA estimation. It not onlyreduces the computational consumption to less than 1/3 of the existing methods,but also can partially eliminate the directions of interference noises. In a real-istic conference room, experiment results of the localization system, composedof 7 microphones, show that: with and without searching space pre-estimationprocessing, the maximal error of DOA estimate is 4.4? and 11.4?, respectively.(4) Proposed a first-order di?erential microphone (FDM) array based spectral do-main speech enhancement method. This method applies dual-microphone FDMarray, in combination with single-channel spectral enhancement techniques, thusit can obtain an estimation of speech spectrum and noise spectrum simultane-ously, while correcting the noise spectrum in real time. Compared with thepresent dual-channel speech enhancement techniques, this method can achieve2dB～6dB output SNR gain, and reduce the computational complexity by 2/3.