Acoustic characteristics related to the perceptual pitch in whispered vowels

The characteristics of whispered speech are not well known. The most remarkable difference from ordinal speech is the pitch (the height of speech), since whispered speech has no fundamental frequency. In this study, we have tried to reveal the mechanism of producing pitch in whispered speech through an experiment in which a male and a female subjects uttered Japanese whispered vowels in a way so as to tune their pitch to the guidance tone with different five to nine frequencies. We applied multivariate analysis such as the principal component analysis to the data in order to make clear which part of frequency contributes much to the change of pitch. We have succeeded in endorsing the previous observations, i.e. shift of formants is dominant, with more detailed numerical evidence. In addition, we obtained some implications to approach the pitch mechanism of whispered speech. The main result obtained is that two or three formants of less than 5 kHz are shifted upward and the energy is increased in high frequency region over 5 kHz.