Abstract: A modified algorithm,in which the bidirectional searching method is used to determine the minima of the noise power spectrum,is proposed based on the improved minima controlled recursive averaging（IMCRA） algorithm. In the proposed algorithm,both minima tracking methods of forward searching and backward searching are utilized together.And the advantages of the two searching methods are combined to increase the accuracy of noise estimator and reduce the delay of the noise minima tracking.The simulated experiments indicate that in nonstationary noise environments and under lower SNR conditions,the proposed approach is very effective.In particular,compared to IMCRA,it obtains a higher improvement in the segmental SNR.