Intensity discrimination as a function of stimulus level with electric stimulation

Relative intensity difference limens (DLs), or Weber fractions, were evaluated as a function of stimulus level, using bipolar pulsatile stimuli. It was undertaken to address several general issues: First, given the wide range of electric DLs reported by previous studies, using a variety of psychophysical methods and stimulation schemes, there was a need to determine whether such large differences could be demonstrated, either across subjects or across electrodes in a particular subject, when psychophysical method and stimulation scheme were held constant. Second, there was a need to determine how Weber fractions change across the dynamic range, so that comparisons could be made to acoustic Weber fractions in normal-hearing listeners. Finally, a more definitive knowledge of Weber fractions in individual implant subjects was needed to evaluate the appropriateness of various compression schemes used in the design and fitting of cochlear implant processors.