IMPROVED NOISE REDUCTION WITH PITCH-ENABLED VOICE ACTIVITY DETECTION

In this paper, we address the problems in standard noise reduction method, which was designed by ETSI (European Telecommunication Standards Institution) for distributed speech recognition. In ETSI-based procedure, noise spectrum is estimated from noise frames, which are detected by a voice activity detector (VAD). Frame energy from the input signal is calculated by the VAD, and if the frame energy is smaller than a threshold, the corresponding frame is considered as noise frame. In highly corrupted noisy signal, this leads VAD towards false detection of a noise frame as a speech frame. Again in the second stage of ETSI-based procedure, the gain factorization coefficient is set to 0.8 for noise frames. This causes less noise reduction for high noisy signal. In our proposed improvement, pitch information along with frame energy is introduced to detect speech and noise frames, and gain factor is increased for better noise reduction from noise frames. Experimental results on Aurora-2J database show significant achievement in noise reduction using the proposed improvement over the original ETSI-based noise reduction