Kalcher, M. (2020). Evaluation of a new speech perception test based on Ling sounds in German language for cochlear implant patients [Diploma Thesis, Technische Universität Wien]. reposiTUm. https://doi.org/10.34726/hss.2020.74402
The fitting of cochlear implants is a crucial step in maximizing the hearing performance in cochlear implant recipients. For the person performing the fitting it is necessary to not only receive the subjective feedback by the patients but also to have objective audiometric measures to assess their hearing performance. While there are dedicated tests for speech signals and pure tones, there is no standardized test that combines the two domains by having a frequency specific speech signal as the test stimulus.The Ling-6 sound test offers a solution to combine these two domains by using six phonemes that have most of their spectral energy in characteristic frequency regions, however, there is no standardized version of this test. A study was conducted at the Medical University of Vienna to investigate whether a new speech test based on the Ling-6 sounds is sensitive to large changes in the fitting map of cochlear implant patients. Three of the most commonly used audiometric tests were additionally tested on their sensitivity to the mentioned map manipulations. The three audiometric tests included the Freiburg monosyllable test, the Oldenburg sentence test, and the assessment of aided sound field thresholds. This thesis presents the preliminary results of the described study.The Ling-6 sounds used in this study were synthesized using Klatt synthesis and are based on recordings of each sound spoken by a male German speaker. The synthesized sounds were spectrally analyzed and underwent a pre-evaluation with normal hearing subjects to ensure sufficient sound quality and understandability.The results of the study suggest that the three most commonly used audiometric tests are not very sensitive to large changes in fitting maps. Results for the new Ling-6 sound test showed, however, that manipulations in certain frequency ranges cause characteristic confusions of the Ling-6 sounds. This information might be used in the future to optimize the fitting maps of patients.
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