  Previous speech enhancement methods focus on estimating the short-time
spectrum of speech signals due to its short-term stability. However, these
methods often only estimate the clean magnitude spectrum and reuse the noisy
phase when resynthesize speech signals, which is unlikely a valid short-time
Fourier transform (STFT). Recently, DNN based speech enhancement methods mainly
joint estimation of the magnitude and phase spectrum. These methods usually
give better performance than magnitude spectrum estimation but need much larger
computation and memory overhead. In this paper, we propose using the Discrete
Cosine Transform (DCT) to reconstruct a valid short-time spectrum. Under the
U-net structure, we enhance the real spectrogram and finally achieve perfect
performance.
