Fitting of an analogue cochlear prosthesis--introduction of a new method and preliminary findings

A new method is suggested for the fitting of a broad-band analogue cochlear prosthesis in terms of frequency response adjustment. This 'frequency-stepped sweep' (FSS) method employs a feedback loop including the patient's loudness judgement to determine a frequency response for the patient's sound processor with which a continuous sinusoidal stimulus with constant amplitude and small increments in frequency can be heard equally loud at the most comfortable loudness level. The FSS-method has been successfully used for the fitting of the sound processors of 40 cochlear implant users. An evaluation of the FSS-method through speech tests employing five different frequency response adjustments with two implant patients confirms its appropriateness. The importance of proper fitting in terms of the frequency response adjustment for a cochlear prosthesis based on broad-band analogue stimulation is demonstrated. The necessary accuracy for the frequency response adjustment is approximately +/- 2 to +/- 5 dB (depending on the dynamic range of the patient) over the frequency range between 100 and 3000 Hz. For the proper adjustments no significant difference has been found between the results for a male and a female speaker.