九官鳥音声の物理的特徴

抄録

In order to make it clear what kind of physical characteristics mimic voices of a talking bird mynah has, 111 mimic of a well-trained mynah are analyzed in (1) the intensity pattern of sound wave form, (2) the fundamental frequency contour, (3) the long term spectrum, (4) the spectral envelope peaks of vowels, (5) the time spectral pattern of consonants. And they are compared with those of tutor's voices. (1) Though the intensity patterns of mimic voices are a little bit different from the tutor's, the duration of the pause in the speech sound and the duration of the burst in some stop consonants are very similar to those of tutor's voices. (2) The fundamental frequency contour shows generally good coincidence between them. The fluctuations of fundamental frequency are also found in mimic voices, however, they are comparatively larger than those of tutor's voices. (3) The long term spectrum of mimic vices has a peak around 900 Hz and the slope for the lower frequency part is 2 dB/oct. and -10dB/oct. for higher frequency part. So, the spectral components below 500 Hz are smaller than those of 1 to 3 kHz by 3 to 10dB. (4) As to the first spectral envelope peaks (P_1) appear around 1kHz in every vowel, it seems very hard to categorize five vowels on the P_1-P_2 plane. (5) As to the spectral changes, the transition of the spectral envelope peaks in the range of 1 to 3kHz are found similar to the tutor's though that of P_1 is not so clear. These physical characteristics of mimic voices of mynah bird are supposed to depend not only on its vocalization but also its auditory function, so that some suggestions will be obtained for the studies of speech synthesis and automatic speech recognition. However, some questions still remain as to how mimic voices with different spectral pattern are processed in the human auditory system.