Aerodynamic and Acoustic Events at the Release of Stop and Fricative Consonants
Kenneth Noble Stevens · The Journal of the Acoustical Society of America · 1971
The production of stop and fricative consonants is characterized by (1) rapid mechanical movements at the supraglottal constriction and at the larynx, (2) changes in intraoral pressure and airflow, and (3) a sequence of acoustic events involving turbulence noise generation and glottal exictation of the vocal tract. A theoretical model that accounts for the observed events at the mechanical, aerodynamic, and acoustical levels is developed. This model consists of an acoustic tube with two time-varying constrictions—one at the glottis and one at the point of articulation of the consonant. The airflow and the turbulence noise generated at the constriction are determined from equations of aeroacoustics, and the conditions under which vocal-cord vibration is initiated are established on the basis of theories of vocal-cord operation. The model has been used to make calculations of airflow, pressure, and acoustic output for several classes of voiced, aspirated, and glottalized stop and fricative consonants. The calculations suggest that these consonants fall into natural classes with well-defined and stable acoustic correlates, based on whether the glottis is in a normal, spread, or constricted configuration and whether the vocal cords are stiff or slack. [Supported by NIH and by the U. S. Air Force.]