I examined the basic psychophysical cues of bilateral electric stimulation that are fundamental in the design of bilateral cochlear implant devices. I found that bilateral cochlear implant users may be able to exploit binaural cues and, therefore, enjoy the benefits associated with binaural hearing.
Speech cues add linearly: 16 normal-hearing subjects listened to stimuli processed using a cochlear implant simulation. Speech in noise was processed with a 12-channel cochlear implant simulation. The speech information was presented such that the signals in the two ears occupied different frequency bands: the 6 odd channels were presented to the left ear and 6 even channels were presented to the right. In the "Left-odd" case, the 6 odd channels were presented to the left ear alone. In the "Right-even" case, the 6 even channels were presented to the right ear alone. In the "Full Diotic" case, all 12 channels were presented to both ears. The sum of the left-odd and right-even information transmission equals that of the interleaved presentation. This shows that subjects listening to a cochlear implant simulation are able to combine the cues received at either ear in an optimal way.
My present research examines how signals are perceptually grouped by cochlear implant users and by normal-hearing subjects. My goal is to gain a better understanding of the processing done by the brain in both types of listeners and to use this to determine how speech understanding by cochlear implant users can be improved, particularly in noisy environments.
The SHBT program was a great gift and a wonderful opportunity for me. In the year I joined the program, time was filled up with enlightening surprises as I applied my electrical engineering training to the understanding of human auditory processing and speech production. In the fall of my second year, I became fascinated by the brainstem processing of auditory stimuli. I persuaded my advisors Dr. Donald Eddington and Dr. Steve Colburn to help me fuse my interest in brainstem processing with my interest in cochlear implants and to start researching bilateral cochlear implants.
