Stochastic beamforming for cochlear implant coding

Robert P. Morse, Stephen D. Holmes, Boris Shulgin, Alexander Nikitin, Nigel G. Stocks

Research output: Chapter in Book/Published conference outputConference publication


Cochlear implants are prosthetic devices used to provide hearing to people who would otherwise be profoundly deaf. The deliberate addition of noise to the electrode signals could increase the amount of information transmitted, but standard cochlear implants do not replicate the noise characteristic of normal hearing because if noise is added in an uncontrolled manner with a limited number of electrodes then it will almost certainly lead to worse performance. Only if partially independent stochastic activity can be achieved in each nerve fibre can mechanisms like suprathreshold stochastic resonance be effective. We are investigating the use of stochastic beamforming to achieve greater independence. The strategy involves presenting each electrode with a linear combination of independent Gaussian noise sources. Because the cochlea is filled with conductive salt solutions, the noise currents from the electrodes interact and the effective stimulus for each nerve fibre will therefore be a different weighted sum of the noise sources. To some extent therefore, the effective stimulus for a nerve fibre will be independent of the effective stimulus of neighbouring fibres. For a particular patient, the electrode position and the amount of current spread are fixed. The objective is therefore to find the linear combination of noise sources that leads to the greatest independence between nerve discharges. In this theoretical study we show that it is possible to get one independent point of excitation (one null) for each electrode and that stochastic beamforming can greatly decrease the correlation between the noise exciting different regions of the cochlea. © 2007 Copyright SPIE - The International Society for Optical Engineering.
Original languageEnglish
Title of host publicationNoise and fluctuations in biological, biophysical, and biomedical systems
EditorsSergey M. Bezrukov
Number of pages9
ISBN (Print)978-0-8194-6739-3
Publication statusPublished - 21 May 2007
EventNoise and fluctuations in biological, biophysical, and biomedical systems - Firenze, Italy
Duration: 21 Jan 200723 Jan 2007

Publication series

NameSPIE proceedings
ISSN (Print)0277-786X


ConferenceNoise and fluctuations in biological, biophysical, and biomedical systems

Bibliographical note

Robert P. Morse ; Stephen D. Holmes ; Boris Shulgin ; Alexander Nikitin and Nigel G. Stocks, "Stochastic beamforming for cochlear implant coding", Proc. SPIE 6602, Noise and Fluctuations in Biological, Biophysical, and Biomedical Systems, 66020U (June 15, 2007); doi:10.1117/12.725416

Copyright 2007 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.


  • cochlear implant
  • stochastic resonance
  • beamforming
  • noise


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