On differential limen of word-based local speechrate variation in Japanese expressed by duration ratio

Fundamental studies about differential limen (DL) for word-based speech rate variations in Japanese are described. In our previous study, the DLs are expressed by subtractive difference of mora duration. In this report, however, to fit the expression for various global speech rate, the DLs are expressed by variation ratio of mora duration. We carry out auditory tests with stimuli made by equally lengthening or shortening a duration of a word in a sentence. The subjects’ focus of attention is diffused to get DLs that are used in the normal natural conversations. The obtained DLs are approximately 0.85 for acceleration and 1.18 for deceleration in variation ratio of mora duration.