The University of Southampton
University of Southampton Institutional Repository

Binaural hearing with a synchronised bilateral cochlear implant system in adult users

Binaural hearing with a synchronised bilateral cochlear implant system in adult users
Binaural hearing with a synchronised bilateral cochlear implant system in adult users
Most bilateral cochlear implant (CI) users have horizontal sound-source localisation and speech perception in noise that is better than that of unilateral CI users and worse than that of normal-hearing listeners. The discrepancy between bilateral CI users and normal-hearing people is thought to partly represent technical limitations in current CI signal processing, which hinders the use of interaural time and level differences. One such limitation is the independent and unsynchronised signal processing in the two CIs. The Digisonic® SP Binaural (DSPB) CI aims to improve binaural hearing by providing synchronised processing of the acoustical inputs, using a single speech processor and two microphones. Two further studies have been published since the commencement of this research project on the spatial hearing ability of DSPB users. Although both these studies concluded that both horizontal sound-source localisation and speech perception in noise can be accessible though the DSPB CIs, consistently with what is provided by conventional bilateral CIs, these studies have some limitations that may have influenced their conclusions. For example, the way the localisation data of their subjects were analysed does not help to determine whether DSPB CI subjects can localise sounds at better than expected from guessing and whether their localisation ability is based on interaural cues or monaural cues introduced by the head shadow. Spatial benefits for speech perception were also not fully reported by the previous studies. The aim of the studies reported in this thesis was to address the limitations of the previous studies and explore in more depth the spatial benefits of the DSPB CIs.

The spatial benefits experienced by eight DSPB CI subjects were assessed in horizontal sound-source localisation, speech perception in noise and self-reported measures. Their ability was also compared to eight unilateral CI subjects, who were chosen as likely to be representative of the better unilateral CI performers. Results showed that the majority of the postlingually deaf DSPB subjects could localise sounds at a better than chance range, defined by unbiased and biased guessing, which seems similar to previous results with conventional bilateral CI adults. Although the results for unilateral CI subjects indicate that monaural cues may provide some useful information for localisation, such cues were found to provide lower localisation accuracy than binaural cues provided by DSPB implants. Speech perception thresholds were also assessed with the speech and noise spatially co-located and separated. Results showed that, as with unilateral CI subjects, the DSPB subjects were not able to take advantage of separating speech from noise for speech perception. Results from the Speech, Spatial and Qualities of Hearing Scale indicated better self-reported spatial hearing ability for the DSPB than unilateral CIs groups, although it was not statistically significant. It is concluded that the DSPB CIs seem to provide advantages for horizontal localisation over unilateral CIs for the majority of postlingually deaf DSPB adults. There is, however, no evidence that the way the processing is synchronised in the DSPB CIs can offer any advantages over conventional bilateral CIs for localisation.
Alothman, Noura
b2828b24-245d-41ba-86e1-1c86d24a91fd
Alothman, Noura
b2828b24-245d-41ba-86e1-1c86d24a91fd
Rowan, Daniel
5a86eebe-53da-4cd2-953e-e3ca1ae61578

Alothman, Noura (2016) Binaural hearing with a synchronised bilateral cochlear implant system in adult users. University of Southampton, Faculty of Engineering and the Environment, Doctoral Thesis, 320pp.

Record type: Thesis (Doctoral)

Abstract

Most bilateral cochlear implant (CI) users have horizontal sound-source localisation and speech perception in noise that is better than that of unilateral CI users and worse than that of normal-hearing listeners. The discrepancy between bilateral CI users and normal-hearing people is thought to partly represent technical limitations in current CI signal processing, which hinders the use of interaural time and level differences. One such limitation is the independent and unsynchronised signal processing in the two CIs. The Digisonic® SP Binaural (DSPB) CI aims to improve binaural hearing by providing synchronised processing of the acoustical inputs, using a single speech processor and two microphones. Two further studies have been published since the commencement of this research project on the spatial hearing ability of DSPB users. Although both these studies concluded that both horizontal sound-source localisation and speech perception in noise can be accessible though the DSPB CIs, consistently with what is provided by conventional bilateral CIs, these studies have some limitations that may have influenced their conclusions. For example, the way the localisation data of their subjects were analysed does not help to determine whether DSPB CI subjects can localise sounds at better than expected from guessing and whether their localisation ability is based on interaural cues or monaural cues introduced by the head shadow. Spatial benefits for speech perception were also not fully reported by the previous studies. The aim of the studies reported in this thesis was to address the limitations of the previous studies and explore in more depth the spatial benefits of the DSPB CIs.

The spatial benefits experienced by eight DSPB CI subjects were assessed in horizontal sound-source localisation, speech perception in noise and self-reported measures. Their ability was also compared to eight unilateral CI subjects, who were chosen as likely to be representative of the better unilateral CI performers. Results showed that the majority of the postlingually deaf DSPB subjects could localise sounds at a better than chance range, defined by unbiased and biased guessing, which seems similar to previous results with conventional bilateral CI adults. Although the results for unilateral CI subjects indicate that monaural cues may provide some useful information for localisation, such cues were found to provide lower localisation accuracy than binaural cues provided by DSPB implants. Speech perception thresholds were also assessed with the speech and noise spatially co-located and separated. Results showed that, as with unilateral CI subjects, the DSPB subjects were not able to take advantage of separating speech from noise for speech perception. Results from the Speech, Spatial and Qualities of Hearing Scale indicated better self-reported spatial hearing ability for the DSPB than unilateral CIs groups, although it was not statistically significant. It is concluded that the DSPB CIs seem to provide advantages for horizontal localisation over unilateral CIs for the majority of postlingually deaf DSPB adults. There is, however, no evidence that the way the processing is synchronised in the DSPB CIs can offer any advantages over conventional bilateral CIs for localisation.

Text
Final e-thesis for e-prints Alothman 21794634.pdf - Other
Download (5MB)

More information

Published date: January 2016
Organisations: University of Southampton, Inst. Sound & Vibration Research

Identifiers

Local EPrints ID: 398618
URI: http://eprints.soton.ac.uk/id/eprint/398618
PURE UUID: 154c1a19-67a2-488c-9ecb-cec476606ea5
ORCID for Daniel Rowan: ORCID iD orcid.org/0000-0002-7190-9997

Catalogue record

Date deposited: 01 Aug 2016 12:55
Last modified: 15 Mar 2024 03:14

Export record

Contributors

Author: Noura Alothman
Thesis advisor: Daniel Rowan ORCID iD

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.

×