IMCRA(Improved?Minima Controlled Recursive Averaging，IMCRA)，它们虽然保证了噪声谱估计的准确性，但在追踪带噪语音平滑功率谱最小值时采用了固定时间窗，因此，在噪声突变的情况下，估计的噪声谱存在很长的延时。(IMCRA, Although they ensure the accuracy of noise spectrum estimation, they use a fixed time window to track the minimum value of smooth power spectrum of noisy speech. Therefore, in the case of noise mutation, the estimated noise spectrum has a long time delay.)