Development of a unified sound processing strategy for combined electric and acoustic auditory stimulation

A hearing aid restores hearing by sound amplification, while a cochlear implant is surgically implanted and restores hearing by electrical stimulation of the auditory nerve. An increasingly common solution to severe hearing loss is a "bimodal system": a cochlear implant in one ear and a hearing aid in the other. By giving the ability to hear with two ears – so-called "binaural hearing" – this set-up could in theory allow its users to figure out where sounds come from, like normal-hearing people do. Unfortunately, in many cases this skill is almost completely absent in people with this bimodal system. This is problematic, as they could otherwise disentangle different simultaneous sounds based on their perceived locations, for example to decipher speech in noisy environments, such as a party or a restaurant. 

This doctoral research is divided in two main parts. In the first part, we present a framework that we established to investigate the binaural mechanisms in speech perception. We apply it in particular to better understand the deficits in people with a cochlear implant and a hearing aid. In the second part, we present a novel sound processing algorithm to improve binaural hearing, which we called head shadow enhancement. We found that our algorithm could improve localization of sounds and speech understanding in noise for bimodal listeners.