Assessment of electronic aids for the hearing impaired which transmit visible or tactile speech

Many electronic aids for the hearing impaired have been developed for the purpose of transmitting information as a visible or tactile speech. However, since the performance of such aids used to be individually evaluated with some restricted materials uttered by one or a few speakers, a variety of the results have been obtained even in almost the same kinds of aids. In order to investigate the most useful information to be transmitted, a common method in the assessment should be established. We propose, in this paper, a new method which uses synthetic speech (isolated and connected vowels) as speech materials. In this method, similarity between images obtained with the aids and with the normal auditory sense is adopted as an important factor for the assessment. The similarity is estimated by labelling test using the systematically changed stimuli sets. This method was applied to the four kinds of visual/tactual aids. As a result, the goodness of vowel information transmitted by each aid manifested itself in a general sense.