Gerald S. Berke
VA Med. Ctr., West Los Angeles, Audiol. & Speech Pathol. 126), Wilshire & Sawtelle Blvds., Los Angeles, CA 90073 and Div. of Head/Neck Surgery, UCLA School of Medicine, Los Angeles, CA 90024
The study of voice quality is built largely upon the assumption of vocal (quasi-)periodicity. Supraperiodic phonation types challenge traditional concepts of vocal periodicity, and thus are of theoretic and practical importance, especially when measuring or describing pathologic vocal function. Unfortunately, the literature describing such phonation is confusing. It has been argued [Gerratt et al., J. Acoust. Soc. Am. Suppl. 1 83, S66 (1988)] that the traditional term ``diplophonia'' has been applied to two distinct phonation types. In one (true diplophonia), the two vocal folds vibrate at different rates, producing a waveform resembling a high-frequency wave modulated by a lower frequency envelope. In the second phonation type (``bicyclicity''), a pattern of two cycles repeats; cycles within the pattern differ in period and/or amplitude, giving a big--small--big--small appearance to the waveform. To investigate the perceptual characteristics of these phonation types, sets of male and female voices were constructed that included equal numbers of diplophonic, bicyclic, and noisy voices. Expert listeners judged the dissimilarity of pairs of these voices. Multidimensional scaling analyses confirmed that bicyclicity and diplophonia are easily distinguished from each other and from rough or breathy voices. Psychoacoustic studies examining factors underlying the nature of the bicyclic and diplophonic percepts will also be described. Implications of findings for periodicity-dependent models of laryngeal function will be discussed. [sup a)]Also at Bell-Northern Res., Verdun, PQ H3E 1H6, Canada.