  Two-stage pipeline is popular in speech enhancement tasks due to its
superiority over traditional single-stage methods. The current two-stage
approaches usually enhance the magnitude spectrum in the first stage, and
further modify the complex spectrum to suppress the residual noise and recover
the speech phase in the second stage. The above whole process is performed in
the short-time Fourier transform (STFT) spectrum domain. In this paper, we
re-implement the above second sub-process in the short-time discrete cosine
transform (STDCT) spectrum domain. The reason is that we have found STDCT
performs greater noise suppression capability than STFT. Additionally, the
implicit phase of STDCT ensures simpler and more efficient phase recovery,
which is challenging and computationally expensive in the STFT-based methods.
Therefore, we propose a novel two-stage framework called the STFT-STDCT
spectrum fusion network (FDFNet) for speech enhancement in cross-spectrum
domain. Experimental results demonstrate that the proposed FDFNet outperforms
the previous two-stage methods and also exhibits superior performance compared
to other advanced systems.
