Speech sound misperceptions for children and adults with cochlear implants

Introduction: By using nonword speech sound identification tests (SSIT) in the assessment of the benefit from cochlear implants (CI), one avoids semantic influence on identification. The objectives of this study are to evaluate a new SSIT for both cochlear implanted (CI) and normal-hearing (NH) children and adults and to assess the speech sound identification score for both the CI and NH groups. Methods: The SSIT is conducted by playing consonant-vowel-consonant (CVC) and vowel-consonant-vowel (VCV) nonwords to the participants in an anechoic chamber. Recordings of the participants' repetitions are transcribed phonetically by two independent trained phoneticians. Participants are NH adults (16 years and above), NH six-year-olds, adult CI-users and children with CI. All participants have to have perfect pronunciation of all the Norwegian speech sounds and to pass the other inclusion criteria. The SSIT will also be conducted on Afrikaans-speaking CI patients at Tygerberg hospital in Cape Town, South Africa. The results will be compared with similar results obtained at Oslo university hospital in Oslo, Norway. Preliminary results did not show any ceiling effect of the SSIT score for NH. Thus the test proved to be difficult but feasible for NH participants. For the CI users, the SSIT score turned out to be approximately 50%, which gave a desirable discrimination slope. Knowledge of which speech sound misperceptions are the most typical, is important both for the clinical physicists who do the fitting of the speech processor, and who by optimizing the programming of the speech processor can improve how well the cochlear implanted patients can identify speech sounds, the teachers of the deaf and speech therapists who train the CI-users in listening and articulation, researchers trying to improve the existing as well as develop new CI stimulation strategies and the authorithies in Norway, who do not grant money for bilateral cochlear implantation.