Lifespan anatomic and vowel acoustic studies confirm prepubertal sexual dimorphism of the human vocal tract and absence of lengthening in aging

Abstract

To study anatomic-acoustic relations across the lifespan, anatomic studies of the developing vocal tract (VT) using medical imaging studies were related to vowel acoustic space as synthesized from published data. However, the aggregate acoustic data highlighted the need to acquire sex-specific vowel acoustic data across the lifespan using controlled methodology for data collection and analysis; also, to acquire measurements of the higher formants. Lifespan anatomic and acoustic (4-to-92 years) data helped resolve two questions. First, anatomic studies revealed significant prepubertal sex differences in the oral region of the VT (3-to-7 years) that are masked by growth rate differences between males and females. Three-dimensional anatomic findings also revealed prepubertal sexual dimorphism in select regions of the mandible and pharynx. Second, anatomic findings confirmed that VT length does not increase with aging. Acoustic studies similarly confirmed sex differences in fundamental frequency emerging at age 7; and the presence of significant prepubertal sexual dimorphism of the higher formant frequencies (F3-F4) at the earliest age studied (4 years). Findings for adults showed significant age-related decreases in fundamental frequency in women only, and no changes in formant frequencies in either sex across several decades. The results underscore the importance of sex-specific and non-uniform growth of the VT structures. [NIDCD funding support R01DC006282.]