Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session G39: Bio: Phonation and Speech |
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Chair: Michael Krane, Pennsylvania State University Room: Portland Ballroom 256 |
Monday, November 21, 2016 8:00AM - 8:13AM |
G39.00001: Aerosol Emission during Human Speech Sima Asadi, William Ristenpart The traditional emphasis for airborne disease transmission has been on coughing and sneezing, which are dramatic expiratory events that yield easily visible droplets. Recent research suggests that normal speech can release even larger quantities of aerosols that are too small to see with the naked eye, but are nonetheless large enough to carry a variety of pathogens (e.g., influenza A). This observation raises an important question: what types of speech emit the most aerosols? Here we show that the concentration of aerosols emitted during healthy human speech is positively correlated with both the amplitude (loudness) and fundamental frequency (pitch) of the vocalization. Experimental measurements with an aerodynamic particle sizer (APS) indicate that speaking in a loud voice (~95 decibels) yields up to fifty times more aerosols than in a quiet voice (~75 decibels), and that sounds associated with certain phonemes (e.g., [a] or [o]) release more aerosols than others. We interpret these results in terms of the egressive airflow rate associated with each phoneme and the corresponding fundamental frequency, which is known to vary significantly with gender and age. The results suggest that individual speech patterns could affect the probability of airborne disease transmission. [Preview Abstract] |
Monday, November 21, 2016 8:13AM - 8:26AM |
G39.00002: Flow-Structure-Acoustic Interaction Simulation of Vocalization of a Non-song Bird. Weili Jiang, Xudong Zheng, Qian Xue, Jeppe Have Rasmussen, Coen Elemans The myoelastic-aerodynamic mechanism of vocalization was recently evidenced in birds across a wide range of taxa, which, for a long time, was believed to generate sound based on the aerodynamic whistle mechanism. The objective of the current study is to: (1) develop a first-principle based, flow-structure-acoustics (FSA) interaction computational model of a non-song bird (rock pigeon); (2) strongly validate the computational model by comparing to the experimental data on the same bird model; (3) examine the data so as to generate new insights into the physics of vocalization of birds. In the current approach, a sharp interface immersed boundary method based incompressible flow solver is utilized to model the air flow; A finite element based solid mechanics solver is utilized to model the LVM(lateral vibratory mass) vibration; A high-order immersed boundary method based acoustics solver is utilized to directly compute sound. Geometric structure of the syrinx, including syringeal lumen, LVM, position of tracheal rings, is based on CT scan of a rock pigeon. The LVM is simulated as isotropic material according to the experimental measurements. Simulation setup about the bronchial pressure, static deformation due to air sac pressure also follows the setup in the experiments. Results including the fundamental frequency, air flow rate, gap, vibration shape will be analyzed and compared to the experimental data. [Preview Abstract] |
Monday, November 21, 2016 8:26AM - 8:39AM |
G39.00003: Direct numerical simulation of human phonation shakti saurabh, Daniel Bodony A direct numerical simulation study of the generation and propagation of the human voice in a full-body domain is conducted. A fully compressible fluid flow model, anatomically representative vocal tract geometry, finite deformation model for vocal fold (VF) motion and a fully coupled fluid-structure interaction model are employed. The dynamics of the multi-layered VF tissue with varying stiffness are solved using a quadratic finite element code. The fluid-solid domains are coupled through a boundary-fitted interface and utilize a Poisson equation-based mesh deformation method. A new inflow boundary condition, based upon a quasi-1D formulation with constant sub-glottal volume velocity, linked to the VF movement, has been adopted. Simulations for both child and adult phonation were performed. Acoustic characteristics obtained from these simulation are consistent with expected values. A sensitivity analysis based on VF stiffness variation is undertaken and sound pressure level/fundamental frequency trends are established. An evaluation of the data against the commonly-used quasi-1D equations suggest that the latter are not sufficient to model phonation. Phonation threshold pressures are measured for several VF stiffness variations and comparisons to clinical data are carried out. [Preview Abstract] |
Monday, November 21, 2016 8:39AM - 8:52AM |
G39.00004: ABSTRACT WITHDRAWN |
Monday, November 21, 2016 8:52AM - 9:05AM |
G39.00005: Does a pneumotach accurately characterize voice function? Gage Walters, Michael Krane A study is presented which addresses how a pneumotach might adversely affect clinical measurements of voice function. A pneumotach is a device, typically a mask, worn over the mouth, in order to measure time-varying glottal volume flow. By measuring the time-varying difference in pressure across a known aerodynamic resistance element in the mask, the glottal volume flow waveform is estimated. Because it adds aerodynamic resistance to the vocal system, there is some concern that using a pneumotach may not accurately portray the behavior of the voice. To test this hypothesis, experiments were performed in a simplified airway model with the principal dimensions of an adult human upper airway. A compliant constriction, fabricated from silicone rubber, modeled the vocal folds. Variations of transglottal pressure, time-averaged volume flow, model vocal fold vibration amplitude, and radiated sound with subglottal pressure were performed, with and without the pneumotach in place, and differences noted. (Acknowledge support of NIH grant 2R01DC005642-10A1.) [Preview Abstract] |
Monday, November 21, 2016 9:05AM - 9:18AM |
G39.00006: Power flow in normal human voice production Michael Krane The principal mechanisms of energy utilization in voicing are quantified using a simplified model, in order to better define voice efficiency. A control volume analysis of energy utilization in phonation is presented to identify the energy transfer mechanisms in terms of their function. Conversion of subglottal airstream potential energy into useful work done (vocal fold vibration, flow work, sound radiation), and into heat (sound radiation absorbed by the lungs, glottal jet dissipation) are described. An approximate numerical model is used to compute the contributions of each of these mechanisms, as a function of subglottal pressure, for normal phonation. (Acknowledge support of NIH grant 2R01DC005642-10A1.) [Preview Abstract] |
Monday, November 21, 2016 9:18AM - 9:31AM |
G39.00007: A budget of energy transfer in a sustained vocal folds vibration in glottis Lucy Zhang, Jubiao Yang, Michael Krane A set of force and energy balance equations using the control volume approach is derived based on the first principles of physics for a sustained vocal folds vibration in glottis. The control volume analysis is done for compressible airflow in a moving and deforming control volume in the vicinity of the vocal folds. The interaction between laryngeal airflow and vocal folds are successfully simulated using the modified Immersed Finite Element Method (mIFEM), a fully coupled approach to simulate fluid-structure interactions. Detailed mathematical terms are separated out for deeper physical understanding and utilization of mechanical energy is quantified with the derived equation. The results show that majority of energy input is consumed for driving laryngeal airflow, while a smaller portion is for compensating viscous losses in and sustaining the vibration of the vocal folds. [Preview Abstract] |
Monday, November 21, 2016 9:31AM - 9:44AM |
G39.00008: A finite element study on the cause of vocal fold vertical stiffness gradient Biao Geng, Qian Xue, Xudong Zheng Vertical stiffness variation (VSV) on the vocal fold medial surface was recently reported and was hypothesized to be an important feature for phonation as it can promote the divergent angle during vibration. However, the underlying mechanism of such feature remains unclear. In our opinion, there are three primary mechanisms that could contribute to the overall stiffness variation, including the material variation in the cover layer, the superior-inferior asymmetry of the vocal fold structure and the presence of the conus elasticus. The current study aims to use the finite element method to quantify the contribution of these three mechanisms to the VSV. The preliminary results showed that the material variation and structural asymmetry can have a significant effect on the VSV, however, the presence conus elasticus had nearly negligible effect. The structural asymmetry due to the subglottal angle caused about 15{\%}\textasciitilde 20{\%} increase in VSV when the subglottal angle beyond 40\textdegree , and its effect was more significant at small subglottal angles. [Preview Abstract] |
Monday, November 21, 2016 9:44AM - 9:57AM |
G39.00009: Glottal jet inertance Michael MPhail, Michael Krane Estimates of an inertive contribution of the glottal jet to glottal aerodynamic resistance is presented. Given that inertance of the flow in a constriction can be expressed in terms of the kinetic energy of the flow, and that a jet is a maximum kinetic energy flow pattern, it is argued that the glottal jet possesses its own inertance which is at least as large as that of the vocal tract. These arguments are supported by estimates of inertance obtained from simulations of an unsteady flow through an axisymmetric orifice, and of a compliant constriction with the approximate shape and mechanical properties of the vocal folds. It is further shown that the inertive effect of the glottal jet depends on the jet path and jet mixing, with a slowly diffusing, symmetric jet showing higher inertance than an asymmetric jet which rapidly mixes with supraglottal air. (Acknowledge support of NIH grant 2R01DC005642-10A1.) [Preview Abstract] |
Monday, November 21, 2016 9:57AM - 10:10AM |
G39.00010: The impact of intraglottal vortices on vocal fold dynamics Byron Erath, Alireza Pirnia, Sean Peterson During voiced speech a critical pressure is produced in the lungs that separates the vocal folds and creates a passage (the glottis) for airflow. As air passes through the vocal folds the resulting aerodynamic loading, coupled with the tissue properties of the vocal folds, produces self-sustained oscillations. Throughout each cycle a complex flow field develops, characterized by a plethora of viscous flow phenomena. Air passing through the glottis creates a jet, with periodically-shed vortices developing due to flow separation and the Kelvin-Helmholtz instability in the shear layer. These vortices have been hypothesized to be a crucial mechanism for producing vocal fold vibrations. In this study the effect of vortices on the vocal fold dynamics is investigated experimentally by passing a vortex ring over a flexible beam with the same non-dimensional mechanical properties as the vocal folds. Synchronized particle image velocimetry data are acquired in tandem with the beam dynamics. The resulting impact of the vortex ring loading on vocal fold dynamics is discussed in detail. [Preview Abstract] |
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