Detecting Japanese local speech rate deceleration in spontaneous conversational speech using a variable threshold

The variable threshold(VT), which detects the speech rate deceleration, is proposed. The VT varies dynamically depending upon the duration of previous mora in the utterance. The VT should not change rapidly because listener cannot perceive small variations of mora duration. Thus, a set of functions with time constants which decide response speed of the VT is introduced. We apply the VT to six sentences of spontaneous conversational speech. The auditory test of detecting local speech rate deceleration is carried out for the evaluation. The possibility of detecting the local speech rate deceleration by the VT is indicated.