Speech enhancement based on the General Transfer function GSC and postfiltering

In speech enhancement applications microphone array postfilteing allows additional reduction of noise components at a beamformer output. Among microphone array structures the recently proposed General Transfer function Generalized Sidelobe Canceller (TF-GSC) has shown impressive noise reduction abilities in a directional noise field, while still maintaining low speech distortion. However, in a diffused noise field less significant noise reduction is obtainable. The performance is even further degraded when the noise is nonstationary . In this contribution we present three postfiltering methods for improving the performance of microphone arrays. Two of which are based on single-channel speech enhancers and making use of recently proposed algorithms concatenated to the beamformer output. The third is a multi-channel speech enhancer which exploits noise-only components constructed within the TF-GSC structure. An experimental study, which consists of both objective and subjective evaluation in various noise fields, demonstrates the advantage of the multi-channel postfiltering compared to the single-channel techniques.