Objectives:
(1) To estimate the dynamic range (DR) for electric stimulation by means of acoustic and electric loudness matching; (2) to characterize loudness growth as a function of electric stimulus amplitude across the DR.

Design:
Prospective study.

Study Design:
Three cochlear implant subjects, with normal hearing in the contralateral ear, participated in this study (ME28, ME-29, ME-30). For each electrode, the upper limit of electric stimulation was loudness matched to three different types of pitch-matched acoustic stimuli. Within the electric DR, the 25%, 50%, and 75% points were loudness matched to the acoustic stimuli to create loudness growth functions.

Results:
ME-28’s DRs for electric stimulation were constant at 17–18 dB across electrodes. ME-29’s and ME-30’s DRs were narrower, at around 10 dB. For ME-28 and ME-30, none of the corresponding DRs for matched acoustic stimuli exceeded 50 dB. Only one of ME-29’s DRs exceeded 35 dB. Loudness growth functions showed a tendency for basal electrodes to have gentler overall slopes. For relatively high proportions of the DR, the three different types of acoustic stimuli tend to have similar loudness growth slopes. However at low levels, the fewer harmonics, the steeper the loudness growth.

Conclusions:
There is qualitative and quantitative agreement but patterns of variation can also be observed.