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  • Research Article
  • Open Access

A Two-Microphone Noise Reduction System for Cochlear Implant Users with Nearby Microphones—Part II: Performance Evaluation

  • 1Email author,
  • 1, 2,
  • 1,
  • 3,
  • 4 and
  • 1
EURASIP Journal on Advances in Signal Processing20082008:451273

  • Received: 27 November 2007
  • Accepted: 20 March 2008
  • Published:


Users of cochlear implants (auditory aids, which stimulate the auditory nerve electrically at the inner ear) often suffer from poor speech understanding in noise. We evaluate a small (intermicrophone distance 7 mm) and computationally inexpensive adaptive noise reduction system suitable for behind-the-ear cochlear implant speech processors. The system is evaluated in simulated and real, anechoic and reverberant environments. Results from simulations show improvements of 3.4 to 9.3 dB in signal to noise ratio for rooms with realistic reverberation and more than 18 dB under anechoic conditions. Speech understanding in noise is measured in 6 adult cochlear implant users in a reverberant room, showing average improvements of 7.9–9.6 dB, when compared to a single omnidirectional microphone or 1.3–5.6 dB, when compared to a simple directional two-microphone device. Subjective evaluation in a cafeteria at lunchtime shows a preference of the cochlear implant users for the evaluated device in terms of speech understanding and sound quality.


  • Cochlear Implant
  • Auditory Nerve
  • Average Improvement
  • Sound Quality
  • Cochlear Implant User

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Authors’ Affiliations

Department of ENT, Head and Neck Surgery Inselspital, University of Berne, 3010 Bern, Switzerland
Bernafon Inc., 3018 Bern, Switzerland
ENT clinic of the University of Würzburg, 97080 Würzburg, Germany
Clinique O.R.L., Hôpital Universitaire de Genève, 1211 Genève, Switzerland


© Martin Kompis et al. 2008

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.