Toward musical-noise-free blind speech extraction: Concept and its applications

In this paper, we review a blind musical-noise-free speech extraction method using a microphone array that can be applied to nonstationary noise. In our previous study, it was found that optimized iterative spectral subtraction (SS) results in speech enhancement with almost no musical noise generation, but this method is valid only for stationary noise. The proposed method consists of iterative blind dynamic noise estimation by, e.g., ICA or multichannel Wiener filtering, and musical-noise-free speech extraction by modified iterative SS, where multiple iterative SS is applied to each channel while maintaining the multichannel property reused for the dynamic noise estimators. Also, related to the proposed method, we discuss the justification of applying ICA to such signals nonlinearly distorted by SS. From objective and subjective evaluations simulating real-world hands-free speech communication system, we reveal that the proposed method outperforms the conventional methods.