We studied binaural hearing in 4 children who wear a cochlear implant (CI; Nucleus 24 or 22 system) in 1 ear and a hearing aid (HA) in the other. In every child, the average of hearing loss in the unimplated ear ranged from 101 to 105dBHL. Loudness growth measurement showed dissimilarity between CI and HA, both in aided thresholds and in loudness growth characteristics. To verify binaural integration of speech sounds between the ears, we designed binaural distorted speech audiometry, in which 12 words were high-pass or low-pass filtered at 1kHz, and presented to children. To avoid interaural crossing, a speaker was used to CI and an infrared system used to HA. Comparison of performance showed that CI was dominant in the high-frequency band and HA in the low-frequency band. Binaural improvement was appreciable in CI=high-pass condition, HA=low-pass condition. In subjective hearing scales, 3 childern found benefits in binaural hearing. Paradoxically, results indicated that use of CI and HA generated binaural fusion without conflict despite the difference in timbre between devices.
After analyzing speech content over the telephone for 3 months each following training of 3 profoundly hearing-impaired children who underwent telephone communication training forlyear, we found the following similar changes in the speech. During early training, when the children were unable to catch what was said, they threw in words of agreement or made no response, so the conversation could not proceed. After undergoing training, they began to use strategy skills involving asking again, e. g., “Pardon?”, Requests, e. g., “Could you speak slowly?”, and reconfirmation even when they were unable to hear what was said. This prevented conversation from being interrupted and enabled them to maintain a conversation on the telephone without assistance. These strategy skills were provided by the therapist serving as the telephone caller be verbally instructing the children while they were on the telephone. The children first began using simple skills such as asking again and pronunciation awareness, and then duing the latter part of their training, demonstrated more advanced skills such as conjecture and intensive confirmation that encouraged them to think about conversation content. Vocal communication by profoundly hearing-impaired children differs from that of normal children in that it exhibits the characteristic pattern of confirming what is being said and conveying this content to the other party while making frequent use of strategy skills. It is believed that only language training using communication in the method employed here instills in hearing-impaired children a sense of thoughtfulness and consideration of the other party, and makes it possible for such children to acquire these important strategy skills.