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Enhancing voice pitch perception in cochlear implants
Dissertation (MEng (Bioengineering))--University of Pretoria, 2025.
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University of Pretoria
2026
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| _version_ | 1869483727202025472 |
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| access_status_str | Open Access |
| author2 | Hanekom, J.J. (Johannes Jurgens) |
| author_browse | Hanekom, J.J. (Johannes Jurgens) |
| author_facet | Hanekom, J.J. (Johannes Jurgens) |
| collection | Thesis |
| dc_rights_str_mv | © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng (Bioengineering))--University of Pretoria, 2025. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/107732 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-07-01T04:03:35.572Z |
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| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/107732 Enhancing voice pitch perception in cochlear implants Hanekom, J.J. (Johannes Jurgens) u20446064@tuks.co.za Maina, Sandra-Chie UCTD Sustainable Development Goals (SDGs) Cochlear implants Psychoacoustics Voice pitch Pitch perception Group delays Dissertation (MEng (Bioengineering))--University of Pretoria, 2025. Cochlear implants (CIs) are among the most successful sensory prostheses in the world, partially restoring hearing and, to many users, speech perception. However, they suffer in more complex tasks such as pitch perception. In particular, poor voice pitch perception affects CI users’ ability to perceive information necessary for contextual cues in speech, such as emotion, speaker gender, and speech intonation. This dissertation proposes three speech processing strategies designed to enhance pitch perception, and more critically, voice pitch perception. Although many pitch-enhancing schemes have improved pitch perception for CI users, their evaluation is conducted with harmonic tones or sung vowels, with added speech recognition tests to determine whether speech intelligibility is maintained. This study, instead, focuses on the perception of pitch in the context of speech to determine whether clinical standard strategies, such as ACE, are acceptable in presenting necessary voice pitch cues for non-lexical speech comprehension, as well as whether any of the proposed strategies can improve the presentation of these voice pitch cues without disrupting intelligibility or sound quality. The proposed strategies are adapted from the F0Mod strategy and are designed not only to enhance pitch but also to determine important characteristics of pitch presentation for the design of future processing strategies. The results of the perceptual experiments showed, as expected, that ACE performs well in speech recognition tasks, in quiet, providing pleasant and clear sound quality with minimal interference. However, ACE performs poorly in voice pitch perception tasks. Speech intonation recognition and voice pitch ranking capabilities are poor with this speech processing strategy, especially in noise. Therefore, ACE does not provide the necessary cues needed for full speech comprehension and must be improved. In contrast, the F0Mod strategy, particularly Milczynski et al. (2009)’s adaptation, provides good voice pitch perception, allowing for speech intonation recognition capabilities comparable to those of normal hearing listeners. The strategy is both robust to noise and does not degrade speech intelligibility. However, listeners significantly preferred the sound quality of ACE over that of Milczynski’s F0Mod strategy. In contrast, a proposed strategy, the Delay-based F0Mod strategy, was equivalent to Milczynski’s F0Mod strategy in all tasks, but was not significantly less preferred in terms of sound quality to ACE. Additionally, this strategy shows that amplitude modulation done out of phase across channels to present temporal pitch cues does not significantly degrade pitch perception, and may actually improve sound perception over Milczynski’s F0Mod strategy. In addition, the proposed Location-based F0Mod strategy showed some improvement in pitch perception over ACE, particularly at a lower fundamental frequency (F0) range. Although it is fragile in noisy environments and at higher F0 ranges, it may provide stronger temporal cues than either Milczynski’s F0Mod strategy or the Delay-based F0Mod strategy, either by aligning the cues to its corresponding tonotopic place or by only presenting the peaks of the amplitude-modulated signals, thus increasing the depth of the modulation. The strength of the presented temporal cues can be seen through the perceptual bias that was found with this strategy, where listeners perceived the pitch of the presented speech intonation stimuli as lower than with the other pitch-enhancing schemes. Additionally, speech recognition and sound quality were high with this strategy. The Location-based F0Mod strategy has shown the potential of improving pitch perception through presentation of temporal pitch cues to a selected few channels. However, it must be improved to be reliable and robust to interference. Additionally, its design can be used in future work to determine the effect of the location of the presentation of strong temporal cues by selecting different channels to modulate. Finally, while high sensitivity to pitch differences was found with the proposed Rate-based F0Mod strategy at higher frequencies, pitch perception was inconsistent with the presented stimulus and may have been limited by the proposed fundamental limit of temporal pitch. However, it may also have been an unfamiliar pitch percept that was difficult for participants to categorise, which may be improved with training. However, participants found this strategy to be particularly unintelligible and unpleasant, thereby suggesting the superiority of pitch presentation through amplitude modulation. Overall, this study has demonstrated the ineffectiveness of the ACE strategy in providing suprasegmental speech cues and the effectiveness of an amplitude modulation approach to present the necessary pitch cues. Additionally, this study has introduced three voice pitch-enhancing strategies, of which two are promising, that also inform the weight of the principles on presenting temporal pitch cues in electrical hearing and may suggest other benefits when amplitude modulation is not presented in-phase, across channels. The successful implementation of these voice pitch-enhancing strategies is, however, constrained by the successful implementation of a noise robust and real-time F0 estimator. Electrical, Electronic and Computer Engineering MEng (Bioengineering) Restricted Faculty of Engineering, Built Environment and Information Technology SDG-03: Good health and well-being SDG-09: Industry, innovation and infrastructure SDG-10: Reduces inequalities 2026-01-30T08:24:15Z 2026-01-30T08:24:15Z 2026-04 2025 Dissertation * A2026 http://hdl.handle.net/2263/107732 https://doi.org/10.25403/UPresearchdata.31186477 en © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Cochlear implants Psychoacoustics Voice pitch Pitch perception Group delays Enhancing voice pitch perception in cochlear implants |
| title | Enhancing voice pitch perception in cochlear implants |
| title_full | Enhancing voice pitch perception in cochlear implants |
| title_fullStr | Enhancing voice pitch perception in cochlear implants |
| title_full_unstemmed | Enhancing voice pitch perception in cochlear implants |
| title_short | Enhancing voice pitch perception in cochlear implants |
| title_sort | enhancing voice pitch perception in cochlear implants |
| topic | UCTD Sustainable Development Goals (SDGs) Cochlear implants Psychoacoustics Voice pitch Pitch perception Group delays |
| url | http://hdl.handle.net/2263/107732 https://doi.org/10.25403/UPresearchdata.31186477 |