Monopitched expression of emotions in different vowels

Fundamental frequency (F(0)) and intensity are known to be important variables in the communication of emotions in speech. In singing, however, pitch is predetermined and yet the voice should convey emotions. Hence, other vocal parameters are needed to express emotions. This study investigated the role of voice source characteristics and formant frequencies in the communication of emotions in monopitched vowel samples [a:], [i:] and [u:]. Student actors (5 males, 8 females) produced the emotional samples simulating joy, tenderness, sadness, anger and a neutral emotional state. Equivalent sound level (L(eq)), alpha ratio [SPL (1-5 kHz) - SPL (50 Hz-1 kHz)] and formant frequencies F1-F4 were measured. The [a:] samples were inverse filtered and the estimated glottal flows were parameterized with the normalized amplitude quotient [NAQ = f(AC)/(d(peak)T)]. Interrelations of acoustic variables were studied by ANCOVA, considering the valence and psychophysiological activity of the expressions. Forty participants listened to the randomized samples (n = 210) for identification of the emotions. The capacity of monopitched vowels for conveying emotions differed. L(eq) and NAQ differentiated activity levels. NAQ also varied independently of L(eq). In [a:], filter (formant frequencies F1-F4) was related to valence. The interplay between voice source and F1-F4 warrants a synthesis study.