Acoustic and perceptual analysis of vocal registers in children

According to Hirano, Kurita and Nakashima (1983) the vocal fold structure changes continuously from earliest childhood to late adolescence. During pubert), the elastic fibers are differentiated from the deeper collagenous fibers. These changes can be assumed to affect the vocal register function. The pitches at which register transitions occurred were identified perceptually in recordings of 15 ten-year-old children who sustained vowels at different pitches throughout their range. In normal voices two register transitions were observed, one at 466 Hz and one at 831 Hz mean fundamental frequency, or about 25% higher than in adult voices. Children with functional or physiological voice deviations exhibited only one transition at a mean frequency of 415 Hz. INTRODUCTION Vocal register is a highly relevant aspect of the singing voice, but its nature has remained unclear in the sense that many terms and definitions exist. Register has been defined as a "group of like sounds or tone qualities whose origins can be traced to a special kind of mechanical (muscular) action" (Reid, 1983, p 296). Thus the register phenomenon is assumed to be confined to the vocal fold vibration mechanism, excluding the relevance of vocal tract resonances. However, based on experience with a theoretical model of the voice organ, Titze (1988) suggested that resonance is relevant to the register phenomenon. According to his theory, register boundaries occur when subor supraglottal resonances return significant reflections of the glottal pulses to the glottis in an unfavorable phase of their vibration. This means that the phenomenon of vocal register is dependent on the resonatory systems in the trachea and vocal tract as well as on the vocal fold mechanism. Also, the fundamental frequencies at which register transitions occur can be expected to differ depending on tracheal dimensions. According to Hirano, Kurita and Nakashima (1983) the mechanical properties of the vocal folds change continuously during growth up to about 20 years of age. In infants, the vocal folds are 2 3 mm long, the membranous part being 1.3 2.0 mm and the lamina propria portion of the vocal fold is thick and not layered. The differentiation of the various layers of the lamina propria continues through puberty, thus separating it into three basic layers the looser superficial layer, the intermediate elastic fibers and the deeper layer of collagenous fibers. Obviously, these changes can be assumed to affect vocal register function. * Dept. of Speech Pathology, Danderyd hospital, S-182 88 Danderyd, Sweden ** Dept. of Speech Comtnunication and Music Acoustics, KTH, S-100 44 Stockholm, Sweden