In this paper

we study three types of noisy speech enhancement algorithms based on Minimum Mean-Square Error Short-Time Spectral Estimation: Spectral Amplitude Estimation （MMSE-STSA）

LOG-Spectral Amplitude Estimation （LOG-MMSE-STSA）. and Relative Spectral Amplitude Estimation （MMSE-REL-STSA）. On the basis of theoretical analysis

experimental studies are conducted. Computer simulations show that SNR improvement of 3.4-12dB can be obtained after enhancement processing when the original SNR of noisy speech degraded by Additional White Gaussian Noise ranges from 5dB to-10dB. Among the three algorithms

MMSE-LOG-STSA provides the best SNR improvement

and the SNR results coincide with informal listening.We also study the reduction of residual noise accompanied by the enhanced speech. By using the center clipping and gain function modification of estimator

the residual noise can be reduced significantly.