Mediterr J Otol 2005:1(2):87-93.

A novel stimulation of cochlear implant in music perception: Fine structure model by using nicstream

Ogut F., Engin EZ., Kilic MA., Dicle Z., M.D., Engin M.
Dept. Oto9laryngology, Ege Univ. Medical Faculty, İzmir, Turkey.  ogut@med.ege.edu.tr

OBJECTIVES: We modified the software ÒNicstreamÓ to increase the quality of the music perception of the Nucleus-24 implant system, and thus, to improve the quality of the music perception in cochlear implant (CI) users by adjusting the cut-off frequency of the filters.

MATERIALS AND METHODS: In this study, Continuous Interleaved Sampling (CIS) and Advanced Combinational Encoder (ACE) digital signal processing strategies for the Nucleus-24 implant system were used. We modified the current software to design a novel stimulation cochlear implant in music perception at the fine structure model with different division of the frequency scale that was based on Helmholtz. We examined a musical melody and eight notes of a musical instrument. First, the music quality of the output files was determined subjectively by five musicians, who listened the output music signals and gave a score for melody, harmony, rhythm, and pitch discrimination of the musical melody and the notes of the musical instrument. A score between 0 (poor result) and 10 (good result) was accorded. Then the sounds were objectively evaluated by signal processing using a software program (Hypersignal) to obtain digitized sonograms.

RESULTS: The scores of melody, harmony and pitch discrimination of the CIS using Helmholtz filter frequencies were considerably higher. Spectrographic analyses and evaluation of the sounds showed that CIS strategy is more appropriate than ACE strategy for CI listeners.

CONCLUSION: To improve the quality of the music perception in CI users, the software of the Nucleus-24 implant system must be modified by adjusting the cut-off frequency of the filters using frequency scales such as Helmholtz. The optimum parameters can be determined for individual musical instruments and different kinds of music.