Hearing Aid
Hearing Aid
People with hearing impairment who use a cochlear implant (CI) and one or two acoustic hearing aids simultaneously generally obtain substantial perceptual benefits in comparison to the use of the CI alone. However, the two types of device are usually fitted independently, and the techniques for processing sounds in each device differ greatly. To obtain most benefit from combined acoustic-electric stimulation, both the fitting of existing devices and the design of future devices need improvement. In particular, the loudness perceived by users of bimodal hearing devices is often dissimilar between the acoustic and electric modalities. For example, sounds that contain dominant high-frequency components can be heard easily via a CI but may be too soft when heard through acoustic hearing aids for the typical configuration of hearing impairment of many device users.
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One potential solution to this problem is to fit a hearing aid incorporating frequency compression to CI users with suitable types of hearing impairment. Previous research in this laboratory led recently to the commercial development by the Swiss company Phonak of hearing instruments that provide an effective frequency-compression function. The present project aims to determine whether the use of frequency compression is beneficial to CI users who have usable acoustic hearing in at least the ear that was not implanted.
A more-general approach to the problem of loudness mismatch between the two types of device is to apply computational models of loudness to improve the compatibility of signals perceived via the acoustic and electric stimulation modalities. Such models can estimate automatically the loudness perceived by the listener when the same sound is heard simultaneously via the CI and the acoustic aids. The outputs of the models can be used to adjust in real time the levels of stimulation presented by each device to optimise the user’s perception when listening with both types of device together.
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