Loudness ratio production by cochlear implantees using the spectral maxima sound processor

The loudness growth characteristics of five users of the Mini System 22 implant and the Spectral Maxima Sound Processor were measured and compared with those of five normally hearing subjects. The main objective was to evaluate the suitability of the function employed in the sound processor that converts acoustic input levels into levels of electrical stimulation. The method of loudness ratio production was used. The average result of the normally hearing subjects for halving and doubling loudness was 10.8 dB. The results of three of the implantees were comparable with those of the normally hearing subjects (average 8.83 dB), while those of the remaining subjects were quantitatively and qualitatively different. Investigation showed that altering the amplitude conversion function in the sound processor would not make the results of these two implantees more like those of the other subjects. However, it is possible that their responses were affected by the limited input dynamic range of the sound processor.