Comparison of Speech Intelligibility Parameter in Cochlear Implants by Spatial Filtering and Coherence Function Methods

This paper evaluates the speech intelligibility parameter of electrical hearing with a Cochlear implant where a multi-electrode array implanted in the cochlea transfers the electrical impulses to the brain. Compared to normal listeners, a CI user requires higher signal to noise ratio for similar speech recognition. Generalized side-lobe cancellers using directional microphones have shown good results when there is a single noise source. But the performance deteriorates as the number of noise sources increase. This paper reviews two techniques one based on spatial filtering and the other based on coherence function and discusses the possibility of combining them for better speech intelligibility as both the methods complement each other. In both the algorithms, estimation of noise is not required and they have the capability of handling multiple sources and speakers. Better intelligibility results were obtained by the researchers using these techniques.