Date of Award
Master of Science
Chiu Tai Law, Chris Yingchun Yuan, Weizhong Wang
Previous Studies for bilateral cochlear implants users examined cocktail -party setting under anechoic listening conditions. However in real world listeners always encounter problems of reverberation, which could significantly deteriorate speech intelligibility for all listeners, independent of their hearing status.
The object of this study is to investigate the effects of reverberation on the binaural benefits for speech recognition by bilateral cochlear-implant (CI) listeners.
Bilateral CI subject was tested under different reverberation conditions. IEEE recorded sentences from one male speaker mixed with either speech shaped noise (ssn), energy masking, or with 2 female competing takers (2fsn), informational masking, at different signal -noise -ratios (SSN) were used as stimuli. The male target speech was always set at 90 degrees; azimuth (from the front), while the masker were placed 0 degrees;, 90 degrees;, 180 degrees; azimuth (0 degrees; implied left, 180 degrees; implied right). Generated stimuli were presented to Bilateral Cochlear Implant subjects via auxiliary input, which was connected to sound processor in a double wall sound attenuated booth. In each condition, subject was tested with individual ear alone, as well as with both ears.
Prior studies predict there would be decrease in speech intelligibility in reverberated condition as compared with anechoic environment. As predicted we saw a decrease in speech intelligibility in reverberated condition as compared with anechoic environment as reverberant environment produce more masking than the less reverberant environment do. We also observed that benefit of spatial hearing in reverberant environment. We observed that when the masking was placed at the better ear the subject performed better than the masking placed the other ear. We also observed the reverberation effect on energetic and informational masking. We observed that when the target and interfere are spatially separated, reverberation had greater detrimental effect on informational masking than energetic masking, and when the target and interfere were co-located the energetic masking results performed better than informational masking.
Due to time limitation and subject availability, test was done with one CI subject. Further testing and research on this topic, would help to understand the effect/s the informational masking vs energetic masking in reverberated conditions.
Bhandary, Moulesh, "Speech Perception in Reverberated Condition By Cochlear Implants" (2014). Theses and Dissertations. 588.