Abstract
It is known that the slowly-varying (4-16Hz) amplitude envelope plays an important role in transmitting speech information. According to the forward masking effect, the threshold of hearing, yet, mil be enlarged by sound pressure of precedent stimuli, suggesting short-term unperceiv able periods in speech waveforms. The goal of this study is, thus, to show the localization of speech carriers over time. Conflict between subjective scores and quantization errors was observed when all the diminished parts in amplitude were changed to 80% of the precedent envelope maxima. Although quantization error was computationally 104%, which was much larger than the allowance (>20-40%), the noise was subjectively inaudible. The results are interpreted as evidence that the envelope maxima and minima in the repeated structure correspond to the key information and the short-term connection with less perception, respectively. We estimate that the inaudible structure amounts to 67.4% at a bandwidth of 80-5,120Hz.
