Hiromi Nagabuchi Kanako Satoh Nobuhiko Kitawaki
NTT Labs., Midori-cho, Musashino-shi, Tokyo, 180 Japan
A method for generating an artificial conversational speech signal as the input test signal in measuring the characteristics of devices operated by speech signals, such as speech detectors, voice switches, and echo controllers is proposed. A state transition model among talkspurt, pause, double-talk, and mutual silence in conversational speech signals was introduced to simulate the statistical characteristics of these states in real conversational speech signals. This model assumed that the cumulative distribution of the duration time in each state is exponential. During talkspurt intervals, an artificial voice was generated using a speech synthesizer that controlled the spectrum and source characteristics independently. This artificial signal generation method can generate a signal with given characteristics by changing the values of system parameters, such as the average duration time of each state, transition probability from one state to another, and LPC (linear predictive coding) parameters that express short-term spectrum variation. The effectiveness of this artificial signal was demonstrated when used to measure the characteristics of a speech detector.