Fluid flow in a dynamic mechanical model of the vocal folds and tract. I. Measurements and theory

Abstract

In this study, aerodynamic and acoustic measurements were obtained in a dynamic mechanical model of the larynx and vocal tract. The model consisted of a uniform duct, intersected by a pair of sinusoidally oscillating shutters. A controlled airflow along the duct was periodically disturbed by the action of the shutters and pressure, and flow velocity measurements were obtained in the region downstream. The velocity field in the duct could be decomposed into three distinct components: a mean flow, a fluctuating acoustic particle velocity, and a fluctuating nonacoustic velocity associated with the transport of vortices along the duct at the local mean flow velocity. Two theoretical models for sound radiation from the duct exit were investigated. The first was based on the in-duct acoustic field alone and was unable to provide a realistic prediction of the measured, radiated sound field except at the first formant of the duct. In the second a simple description of sound generation due to the interaction of vortices with the duct exit was added. In this case much closer prediction of the measured values was achieved, leading to the conclusion that the interaction of the nonacoustic velocity fluctuation with the duct boundaries results in a significant additional source of acoustic energy located in the region of the duct exit.

Unsteady laryngeal airflow simulations of the intra-glottal vortical structures

“…As shown in both experimental and numerical studies, vortical structures affect the voice production through contributions as monopole, dipole, and quadrupole acoustic sources ͑McGowan, 1988; Barney et al, 1999;Titze, 2000;Zhao et al, 2001;Zhang et al, 2004;Suh and Frankel, 2007͒. The monopole acoustic source that is associated with fluid displacement due to acceleration of a moving surface was found to dominate the other acoustic sources at very high vocal fold vibration frequencies ͑Zhao et al, 2002͒, while the dipole acoustic source generated by the pressure distribution ͑fluctuating loading͒ on a surface was found to dominate for convergent-divergent glottal models ͑Zhao et al., 2001, 2002Zhang et al, 2004;Suh and Frankel, 2007͒.…”

Dynamics of temporal variations in phonatory flow

“…Implicit in such arguments is that the dynamics of the flow do not change during 1 cycle, and that the flow changes at time scales commensurate with the wall motion time scale T o . Experimental evidence ͑Berke et al., 1989;Alipour et al, 1995;Mongeau et al, 1997;Barney et al, 1999;Zhang et al, 2002;Krane et al, 2007͒ suggests that these assumptions are not correct. For example, Fig.…”

“…The second, T m , the duration of the middle interval, is given by T m ϳ T o −2T a . Flow measurements ͑Berke et al., 1989;Alipour et al, 1995;Mongeau et al, 1997;Barney et al, 1999;Zhang et al, 2002;Krane et al, 2007͒ shows the ratio T o / T a can be as high as 6. The unsteady acceleration during the flow initiation and shutoff intervals, estimated using the flow time scale T a , then becomes…”

Experimental Analysis of the Characteristics of Artificial Vocal Folds

“…Many investigators have probed the possible contributions of three-dimensional source mechanisms in voice production. [10][11][12][13][14] McGowan 11 maintained that a full three-dimensional description of the fluid velocity field at glottal exit was required to accurately model the voice source. McGowan proposed a flow feedback mechanism, which directly impacted vocal fold dynamics and, hence, sound generation within the larynx.…”