Fitting and evaluating binaural hearing in adults using electric and acoustic stimulation

Background. Advances in the design of the cochlear implant electrode arrays and improved surgical techniques have resulted in the successful preservation of residual hearing after implantation. The preservation of residual hearing following cochlear implantation provides the capacity for combining electrical and acoustic stimulation in the same ear to benefit the listener. The effectiveness of electric and acoustic stimulation in the implanted ear as compared with electrical and acoustic stimulation alone has been consistently demonstrated in the research literature. There is also accumulating research evidence that supports the provision of acoustic stimulation for residual hearing in the implanted ear together with the non-implanted ear of recipients of a unilateral cochlear implant. A variety of approaches have been used in research studies to fit devices that provide electric and acoustic stimulation in either the implanted ear or in opposite ears, however, there is no comprehensive study evaluating binaural fitting strategies in adult cochlear implant users with residual hearing in both ears. Investigation of a fitting procedure that could maximise hearing outcomes for adult recipients who use electric and acoustic stimulation in the implanted ear and acoustic stimulation in the non-implanted ear would be of benefit. Objective. The overarching goal of this thesis is to examine the fitting of devices that combine electric and acoustic stimulation for cochlear implant recipients with residual hearing in both ears. Aims 1. To systematically investigate how to adjust the hearing aid acoustic output in both ears, for adults who use electric and acoustic stimulation in the implanted ear together with acoustic stimulation in the non-implanted ear. 2. To investigate the effect of varying cross-over frequency settings for electric and acoustic stimulation in the implanted ear combined with acoustic stimulation in the non-implanted ear on speech perception in noise, loca