From voice to speech

Cochlear implants (CIs) are auditory prostheses for deaf individuals. The CI speech signal is degraded compared to normal acoustic hearing. This causes difficulties with the perception of speech and voice characteristics, such as emotions, pitch, or vocal-tract length, related to speakers’ height. Speakers’ mean pitch and vocal-tract length together lead to perceived differences between male and female voices. Voice characteristics  help listeners to focus on one speaker to perceive speech while multiple people talk at the same time. The consequences of the degraded CI speech signal on the development of voice and speech perception in CI children and how this development differs from normal-hearing children are unclear. This dissertation investigated how the perception of differences in speakers’ pitch, vocal-tract length, and emotions and the perception of speech in background speech develops in normal-hearing and CI children.My research shows that there is a strong development in the perception of speech in background speech and differences in voice characteristics in normal-hearing children as well as CI children during the school-age years and beyond. This development does not only seem to relate to CI children’s hearing abilities, but also to their cognitive abilities that are not adult-like yet. Furthermore, CI children seem to make better use of the information provided by the degraded CI speech signal than CI adults. This could be caused by differences in brain plasticity and early exposure to the CI signal. Thus, better cognitive abilities lead to better voice and speech perception in both normal-hearing and CI children.

Dissertation: http://hdl.handle.net/11370/104a9c67-485d-4640-a3b3-677ee5469dc9