Stimulus presentation level and speech perception through a single-channel cochlear implant

This study evaluated the effects of stimulus presentation level on 12 adult 3M/House single-channel cochlear implant users' speech perception performance. Dynamic ranges and loudness growth functions were measured for meaningful speech, and performance-intensity functions were plotted for VCV and CVC nonsense stimuli to determine the presentation level(s) that produced maximum speech perception performance for each subject. Considerable variability was found in the subjects' dynamic ranges. Generally, loudness growth functions were steep for subjects having restricted dynamic ranges and more gradual for those having wide dynamic ranges. No single optimal presentation level was determined; instead, a range of levels produced maximum performance for each subject. Mean levels producing peak scores in equivalent dB SPL were 80 for VCVs and 72 for CVCs. Presentation levels producing optimal performance varied with type of speech stimulus.