ENCODING LOUDNESS BY ELECTRIC-STIMULATION OF THE AUDITORY-NERVE

ELECTRIC charge has long been hypothesized to be the effective stimulu s variable that determines loudness evoked by directly stimulating the auditory nerve. This 'equal-charge, equal-loudness' hypothesis predic ts that stimulus amplitude and duration can be traded linearly to prod uce equal loudness. Loudness sensations from threshold to maximum loud ness were measured systematically as a function of stimulus amplitude and duration in cochlear implant listeners. The measured data do not s upport the equal-charge, equal-loudness hypothesis: an increment in st imulus amplitude produces a significantly louder sensation than the sa me change in stimulus duration. Instead of the linear equal-charge mod el, a power-function model successfully predicts the measured data and should be used to encode loudness in electric hearing. (C) 1998 Rapid Science Ltd.