Research

Perception of Interaural Intensity Differences by Cochlear Implant Listeners (IID-CI)

Objective

This project investigated the perception of interaural intensity differences among cochlear implant (CI) listeners in relation to the spectral composition and the temporal structure of the signal.

Method

The perception thresholds (just noticeable differences, JND) of CI listeners were examined using differently structured signals. The stimuli were applied directly to the clinical signal processing units, while the parameters of the ongoing stimulation were closely monitored.

Results

JNDs of IIDs in CI listeners ranged from 1.5 - 2.5 dB for a detection level of 80 percent. The type of stimulus seems to bear little relevance on the detection performance, with the exception of one single type of signal - a pulse train with a frequency of 20 Hz. This means that JNDs of CI listeners are only irrelevantly higher than those of normal hearing listeners. CI implantees are sensitive to IIDs, and the JNDs correlate to a difference in arrival angles ranging from 5-10 degrees. Since the JNDs are within the minimal level widths of the transfer of amplitudes by the CI system, the reduction of level width in future systems seems advisable.

Publication

  • Laback, B., Pok, S. M., Baumgartner, W. D., Deutsch, W. A., and Schmid, K. (2004). “Sensitivity to interaural level and envelope time differences of two bilateral cochlear implant listeners using clinical sound processors,” Ear and Hearing 25, 5, 488-500.