Adaptive Sub band GSC Beam forming using L.Mic-Array for Speech Boost

This book presents the description, design and the implementation of a 4-channel microphone array that is an adaptive sub-band generalized side lobe canceller (GSC) beam former used for video conferencing, hands-free telephony etc., in a noisy environment for speech enhancement as well as noise suppression. The side lobe canceller evaluated with both Least Mean Square (LMS) and Normalized Least Mean Square (NLMS) adaptation. A testing structure is presented; which involves a linear 4-microphone array connected for collect the data. Tests were done using one target signal source and one noise source. In each microphone's, data were collected via with fractional time delay filtering then it is divided into sub-bands and applied GSC to each of the subsequent sub-bands. The overall Signal to Noise Ratio (SNR) improvement is determined from the main signal and noise input and output powers, with signal-only and noise-only as the input to the GSC. The NLMS algorithm signicantly improves the speech quality with noise suppression levels up to 13 dB while LMS algorithm is giving up to 10 dB.