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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Neurosci. | doi: 10.3389/fnins.2019.01206

Interactive evaluation of a music preprocessing scheme for cochlear implants based on spectral complexity reduction

 Johannes Gauer1*,  Anil Nagathil1, Rainer Martin1,  Jan P. Thomas2 and Christiane Völter2
  • 1Faculty of Electrical Engineering and Information Technology, Ruhr-University Bochum, Germany
  • 2Department of Otorhinolaryngology, Head and Neck Surgery, Catholic Hospital Bochum, Germany

Music is difficult to access for the majority of CI users as the reduced dynamic range and
poor spectral resolution in cochlear implants (CI), amongst others constraints, severely impair
the auditory perception. The reduction of spectral complexity is therefore a promising means to
facilitate music enjoyment for CI listeners. We evaluate a spectral complexity reduction method for
music signals based on principal component analysis that enforces spectral sparsity, emphasizes
the melody contour and attenuates interfering accompanying voices. To cover a wide range
of spectral complexity reduction levels the design of a new experimental setup for listening
experiments was required. It allows CI users to select the preferred level of spectral complexity
reduction interactively and in real-time. Ten adult CI recipients with postlingual bilateral profound
sensorineural hearing loss and CI experience of at least six months were enrolled in the study. In
eight consecutive sessions over a period of four weeks they were asked to choose their preferred
version out of ten different complexity settings for a total number of 16 recordings of classical
western chamber music pieces. As the experiments were performed in consecutive sessions we
also studied a potential long term effect. Therefore, we investigated the hypothesis that repeated
engagement with music signals of reduced spectral complexity leads to a habituation effect
which allows CI users to deal with music signals of increasing complexity. Questionnaires and
tests about music listening habits and musical abilities complemented these experiments. The
participants significantly preferred signals with high spectral complexity reduction levels over
the unprocessed versions. While the results of earlier studies comprising only two preselected
complexity levels were generally confirmed, this study revealed a tendency towards a selection
of even higher spectral complexity reduction levels. Therefore, spectral complexity reduction for
music signals is a useful strategy to enhance music enjoyment for CI users. Although there is
evidence for a habituation effect in some subjects, such an effect has not been significant in

Keywords: Cochlear Implants, Signal processing, Music signal enhancement , spectral complexity, Complexity reduction, Auditory distortion

Received: 30 Apr 2019; Accepted: 25 Oct 2019.

Copyright: © 2019 Gauer, Nagathil, Martin, Thomas and Völter. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Johannes Gauer, Faculty of Electrical Engineering and Information Technology, Ruhr-University Bochum, Bochum, Germany,