Subband-Based Spectrogram Fusion for Speech Enhancement by Combining Mapping and Masking Approaches

Deep learning brings effective optimization and significant improvements to speech enhancement (SE). Mapping and masking are currently major approaches in single-channel frequency-domain SE with supervised learning. In this work, we first show that these two approaches are complementary in that mapping is more effective in low-frequency bands, while masking is more suitable in high-frequency bands. This is because the high-frequency bands typically have low energy, so estimating the enhanced spectrogram directly does not make sense. Moreover, learning on the low-energy parts is often annihilated by learning on the high-energy parts during the entire loss calculation. To exploit this complementarity, we propose subband-based spectrogram fusion (SBSF), which combines the spectrogram of low-frequency and high-frequency estimated by different SE models. Experimental evaluations show that the SBSF significantly improved the SE performance.