The University of Southampton
University of Southampton Institutional Repository

Acoustic models of consonant recognition in cochlear implant users

Acoustic models of consonant recognition in cochlear implant users
Acoustic models of consonant recognition in cochlear implant users
Normal-hearing adults have no difficulty in recognising consonants accurately, even in moderately adverse listening conditions. By contrast, users of multichannel cochlear implants have difficulty with the accurate perception of consonants, even in good listening conditions. Cochlear implant users are known to show systematic deficits in recognition of consonant features, with perception of the place feature, which relies on spectral information, being worst. These deficits may be attributed both to signal distortions introduced by the processing of the implants and to other factors, in particular the spectrotemporal distortions which occur at the interface between electrode array and auditory nervous system, including cross-channel interaction. The objective of the work reported here was to attempt to partial out the relative contribution of these different factors to consonant recognition. This was achieved by comparing cochlear implant users’ perceptual errors, analysed in terms of information transmission, with errors made by normal-hearing subjects listening to acoustic models of implant processing, in various conditions. Two initial experiments were undertaken to develop and refine an acoustic model of the Nucleus 24 cochlear implant. Findings from these two experiments informed the design of the main acoustic model experiment, which was undertaken in parallel with a further experiment involving users of the Nucleus 24 device. In both experiments, subjects listened to nonsense syllables with and without the addition of stationary background noise, in three different configurations of implant processing parameters. Additionally, in the acoustic model experiment, a simulation of cross-channel spread of excitation, or “channel interaction”, was varied. Results showed that acoustic model experiments were predictive of the pattern of consonant feature transmission in cochlear implant users with better baseline consonant recognition scores. Deficits in consonant recognition in this subgroup could be explained by the loss of phonemically relevant acoustic information in speech due to the nature of cochlear implant processing, while channel interaction appeared to play a smaller role in accounting for problems in consonant recognition. The work also evaluated the effect of changes in channel number and stimulation rate and failed to find any changes in consonant recognition as these parameters were varied. The lack of a stimulation rate effect was consistent with acoustic measurements of the temporal modulation transfer function of the processor, which showed almost no change across stimulation rates.
Verschuur, Carl
5e15ee1c-3a44-4dbe-ad43-ec3b50111e41
Verschuur, Carl
5e15ee1c-3a44-4dbe-ad43-ec3b50111e41

Verschuur, Carl (2007) Acoustic models of consonant recognition in cochlear implant users. University of Southampton, Institute of Sound and Vibration Research, Doctoral Thesis, 271pp.

Record type: Thesis (Doctoral)

Abstract

Normal-hearing adults have no difficulty in recognising consonants accurately, even in moderately adverse listening conditions. By contrast, users of multichannel cochlear implants have difficulty with the accurate perception of consonants, even in good listening conditions. Cochlear implant users are known to show systematic deficits in recognition of consonant features, with perception of the place feature, which relies on spectral information, being worst. These deficits may be attributed both to signal distortions introduced by the processing of the implants and to other factors, in particular the spectrotemporal distortions which occur at the interface between electrode array and auditory nervous system, including cross-channel interaction. The objective of the work reported here was to attempt to partial out the relative contribution of these different factors to consonant recognition. This was achieved by comparing cochlear implant users’ perceptual errors, analysed in terms of information transmission, with errors made by normal-hearing subjects listening to acoustic models of implant processing, in various conditions. Two initial experiments were undertaken to develop and refine an acoustic model of the Nucleus 24 cochlear implant. Findings from these two experiments informed the design of the main acoustic model experiment, which was undertaken in parallel with a further experiment involving users of the Nucleus 24 device. In both experiments, subjects listened to nonsense syllables with and without the addition of stationary background noise, in three different configurations of implant processing parameters. Additionally, in the acoustic model experiment, a simulation of cross-channel spread of excitation, or “channel interaction”, was varied. Results showed that acoustic model experiments were predictive of the pattern of consonant feature transmission in cochlear implant users with better baseline consonant recognition scores. Deficits in consonant recognition in this subgroup could be explained by the loss of phonemically relevant acoustic information in speech due to the nature of cochlear implant processing, while channel interaction appeared to play a smaller role in accounting for problems in consonant recognition. The work also evaluated the effect of changes in channel number and stimulation rate and failed to find any changes in consonant recognition as these parameters were varied. The lack of a stimulation rate effect was consistent with acoustic measurements of the temporal modulation transfer function of the processor, which showed almost no change across stimulation rates.

Text
P2365.pdf - Other
Download (2MB)

More information

Published date: March 2007
Organisations: University of Southampton, Human Sciences Group

Identifiers

Local EPrints ID: 51152
URI: http://eprints.soton.ac.uk/id/eprint/51152
PURE UUID: dd019c93-827e-46e4-af0a-1d83a834ce04

Catalogue record

Date deposited: 07 May 2008
Last modified: 15 Mar 2024 10:15

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×