TELAGAREDDI S N U V RAMESH , pp. 73. ING/School of Engineering, 2012.
In general, an uncontrolled environment may contain degradation components like background noise, speech from other speakers etc. along with required speech components. It is very tough to concentrate only on speech signals in presence of background noise for normal listeners and hearing impaired persons. The hearing organ is substantially sensitive to interfering noise. This interfering noise itself decreases speech quality and speech intelligibility which in turn causes speech communication troublesome. In many applications, the improved speech enhancement is achieved with beamformer using multiple microphones (microphone array). The main function of any beamformer is to create a beam in the direction of the target and place a spatial null in the direction towards jammer. The aim of this thesis work is to find better beamforming technique which suits for hearing aid and also makes the hearing aid free from howling effect. The work investigates working of different beam forming techniques like Elko’s, Wiener, Maximum SNIR and Delay and Sum beamformer. The performance evaluation of all these beamforming techniques for hearing aid works under various noises like interference, babble, wind, restaurant and white noise. The total thesis work is collaboration of four members. In this, my selection of interest is on Elko’s beamformer, and also on reduction of howling effect with NLMS algorithm.
All the beamformers are implemented in MATLAB and validated with different measurements like Signal to Noise Ratio Improvement (SNRI), Speech Distortion (SD), Noise Distortion (ND) and Perceptual Evaluation of Speech Quality (PESQ). Whereas feedback canceller is validated with Perceptual Evaluation of Speech Quality (PESQ) and Echo Return Loss Enhancement (ERLE), which is also implemented in MATLAB.