Evaluation n method of aural environment and development of method for presentation of auditory signals for older persons and persons with disabilities

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The following three summery were achieved;1. The effect of aging on speech perception This study clearly found two factors related to speech recognition and their aging effect. One is that speech recognition performance can be predicted by signal-to-noise ratio and pure-tone averaged hearing level in noisy environment. The other is that cognitive factors. Speaking rate and number of key words were investigated and found that too slow speaking rate gives listening difficulty and doesn't improve speach intelligibility scores both for young and older listeners. The maximum number of key words which should be in memory for a while should be less than three. The maximum presentation level of spoken announcements was obtained and there is no difference of maximum presentation level between young and older listener.2. Prediction of speech transmission performance of acoustical conditions in rooms and case study of evaluation at railway stations and airports This study presents two indices to predict speech transmission performance in rooms. One is Speech Transmission Index and the other is Useful-to Detrimental ratio. Calculation methods and accuracy of predictions were clearly presented. The examples of sound environment in public spaces are evaluated.3. Auditory signals presenting directions and locations to support activities especially for visually impaired persons in public spaces This study presents the effect of noise and reverberation on sound localization of auditory signals. Some of bird's songs presented better accuracy of sound localization than "Pinpon" sound in noise. However, it was found that the key factor of designing auditory signals is time series of signal. As a result of listening tests, head movement is very important to localize a sound and there is not significant difference of accuracy of sound localization between normal person and person with visual impairment.