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This study measures the acoustic power loss that occurs when an acoustic wave passes through a tube with an abrupt change in area. It is determined that the power loss is proportional to the third power of the velocity amplitude, and that the proportionality coefficient depends upon the area change ratio of the tube. On the other hand, the proportionality coefficient is almost independent of the acoustic impedance and frequency in the 80-250 Hz range. Furthermore, the effect of a tapered tube in reducing the coefficient is experimentally investigated. Based on these experimental results, an empirical estimation method for the acoustic power loss is proposed and validated using a high-pressure-helium-filled tube.

A fluid mechanical, or aeroacoustic, point of view is followed to study possible sources of sound during phonation. Concentration is on two features of the vocal tract during phonation: abrupt area change from the glottis to the vocal tract and the finite length of the vocal tract. With these features, a source of sound distinct from the volume velocity source can be identified and a preliminary account of its effect on the acoustic field given. This source of sound is an oscillating force resulting from an interaction of rotational fluid motion with itself. Because of the schematic nature of the geometry of the model used here, this source may be considerably modified in actual phonation. It is concluded that specification of volume velocity is not enough to specify the source during phonation, even neglecting source-tract interaction.

A plane acoustic wave encountering a small area change in a pipe gives rise to transmitted and reflected waves; an analogous problem occurs in shallow‐water theory when an incident wave encounters a small area change in a channel. Experiments with a hydraulic analog, in which photographs obtained from motion pictures of the unsteady phenomena are used to obtain wave heights, agree with the theoretically predicted transmitted‐wave heights using shallow‐water theory. The value of the hydraulic analog as a flow‐visualization tool in research and as a teaching aid in fluid mechanics and acoustics is reconfirmed.

Previous studies by Hollien have demonstrated the effect of changing fundamental frequency upon the cross‐sectional area of the vocal folds. These earlier investigations, however, were based upon conventional laminagraphic x‐ray techniques which produced a composite image of the vocal folds during their entire complex cycling. The experiment reported in this paper is a replication of the former studies, but utilizes STROL, a stroboscopic laminagraphy device which allows examination of the cross‐sectional area of the folds at 36° phase‐shift intervals throughout the vibratory cycle. In addition, animation of the phase‐shift pictures allows observation of the apparent motion of the vocal cords in cross section. In this study, subjects phonated at a constant intensity at three separate fundamental frequencies. The results support Hollien's earlier conclusions, in that, as fundamental frequency increased, the cross‐sectional area and mean thickness of the folds decreased.

High‐speed laryngeal films were obtained from one normally hearing and four deaf subjects as they produced /ihi/ syllables. Computer assisted frame‐by‐frame analysis indicated that during /h/ productions the deaf subjects frequently achieved glottal areas that were three times greater than the normally hearing speakers'. These findings are consistent with previously reported data [Metz and Whitehead, J. Acoust. Soc. Am. Suppl. 1 68, S114 (1980)]. Additionally, glottal area changes over time associated with the normally hearing subjects' /h/ productions appear to be continuous in nature. Vocal fold abductory movement away from V1 was virtually contiguous with the adductory movement toward V2. In contrast, glottal area changes over time associated with many of the deaf subjects' /h/ productions appear to be discontinuous in nature. Such area changes were characterized by abrupt vocal fold abductory movements away from V1 and plateaus in the area change. The temporal nature of this motion suggests that each ...