Generally

some methods of blind signal processing ignore noise

however

noise affects the performance of algorithms

especially seriously in some areas.This paper provides solutions to the problem that mixing matrix is estimated blindly in Gaussian noise with unknown covariance.Based on Maximum Likelihood estimation

the equations are given for solving the mixing matrix and covariance matrix.Gaussian Mixture Model (GMM) is used to approximate the pdf of sources and results in a practical EM algorithm.Computer simulation shows that this algorithm is convergent and has good performance in low SNR.