Requirements on speech processing hearing aids for the profoundly deaf, some preliminary remarks.

Many severely hard of hearing and profoundly deaf persons seem to get very little help from an ordinary hearing aid. This observation has prompted the development of tactile speech processing aids. These aids should however only be used if it can be shown that the subject has no useful residual hearing. In the case of a profound hearing loss the audiogram might in some cases show tactile sensations in the ear. To get a better estimation of the remaining auditory capacity experiments have been made with frequency discrimination measurements, and with speech tests consisting of rhyming word pairs. Results from these different tests are summarized in relation to an audiogram classification system. Two tactile speech processing aids are described. Evaluation studies with these aids show positive results but these results must be compared with the results that can be obtained with ordinary hearing aids and different types of auditory speech processing hearing aids. The possibility to use extreme auditory recording must also be studied. In this case the transmitted signal is not speech-like and it is possible that this limits their usefulness. Experiments with this type of aids might however give valuable information about how the human perceptual systems process signals derived from the original speech signal.