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题名	自适应抗器声送话器的算法研究
作者	倪志明
学位类别	博士
答辩日期	1999
授予单位	中国科学院声学研究所
授予地点	中国科学院声学研究所
关键词	自适应滤波 自适应噪声抵消 LMS算法 语音 噪声 相干性
中文摘要	自适应噪声抵消是自适应滤波的一种实际应用。系统一般有两路输入，主输入信号是含有噪声干扰的有用信号，参考输入是与主输入信号中的噪声相关的噪声信号，系统输出为噪声被降低后的有用信号。自适应噪声抵消的过程主要由LMS算法来完成，但LMS算法有一个很明显的缺点，即在其计算过程中存在一个剩余均方误差（excess MSE），并且这一误差随着目标信号的功率线性地增加，因此当目标信号有较大的功率波动，特别是对于语音信号的增强时系统的效果会很差。本文主要针对这种情况，对LMS算法作了一些改进，使自适应滤波器权值更新的步长随着系统输出信号功率的变化而变化，功率变大时步长减小，功率减小时步长变大，并通过理论分析表明这样改进后的算法有更好的控制效果。然后通过实验验证了理论上的推导，最后得出结论：对于不同信噪比的语音信号，改进后的LMS算法比原来的算法普遍有更好的增强效果，特别是当输入语音信号的信噪比较高时，这一优势更加明显，实验中还详细比较了不同情况下步长参数对控制效果的影响，采用两个参数α和β共同调节步长μ的变化，得到了较好的效果。在效果评价部分提出了计算语音信号信噪比提高量的一个简单方法，即通过控制前后语音间隙的噪声能量的对比得出结果。
英文摘要	Adaptive Noise Cancelling is an application of adaptive filtering. The system has two inputs and one output, one input is the primary input which contains the desired signal corrupted by additive noise, the other input is reference input which contains the noise signal correlated with the noise in the primary input. The system output contains the desired signal and the attenuated noise. Adaptive Noise Cancelling is generally completed by least mean square (LMS) algorithm, A major disadvantage of the LMS algorithm is its excess mean-squared error (MSE), which increases linearly with the desired signal power. This leads to degrading performance when the desired signal exhibits large power fluctuations and is a serious problem in speech enhancement. In this paper, a modified LMS algorithm with the weighted sum method is discussed. The method is designed to solve the excess MSE problem by reducing the size of the steps in the weight update equation when the desired signal is strong. A theoretic analysis is given, which shows that this modified algorithm can achieve better performance than the former one. Experiments verified the conclusion and demonstrated the effectiveness of the modified algorithm, especially when input speech signal has a high SNR, its advantage is remarkable. The dependence of noise cancellation performance on the step parameters is also considered in the experiments, two parameters α and β are used to control the size of the steps, and get preferable results. To evaluate the performance of the modification, a simple method of calculating the SNR in speech signal enhancement is presented. By comparing the input noise to the output noise energy at the speech interval, the SNR enhancement can be estimated.
语种	中文
公开日期	2011-05-07
页码	56
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/634]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	倪志明. 自适应抗器声送话器的算法研究[D]. 中国科学院声学研究所. 中国科学院声学研究所. 1999.

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