Flow-structure-acoustic interaction in a human voice model

Abstract

For the investigation of the physical processes of human phonation, inhomogeneous synthetic vocal folds were developed to represent the full fluid-structure-acoustic coupling. They consisted of polyurethane rubber with a stiffness in the range of human vocal folds and were mounted in a channel, shaped like the vocal tract in the supraglottal region. This test facility permitted extensive observations of flow-induced vocal fold vibrations, the periodic flow field, and the acoustic signals in the far field of the channel. Detailed measurements were performed applying particle-image velocimetry, a laser-scanning vibrometer, a microphone, unsteady pressure sensors, and a hot-wire probe, with the aim of identifying the physical mechanisms in human phonation. The results support the existence of the Coanda effect during phonation, with the flow attaching to one vocal fold and separating from the other. This behavior is not linked to one vocal fold and changes stochastically from cycle to cycle. The oscillating flow field generates a tonal sound. The broadband noise is presumed to be caused by the interaction of the asymmetric flow with the downstream-facing surfaces of the vocal folds, analogous to trailing-edge noise.

A computational study of asymmetric glottal jet deflection during phonation

“…In the context of phonation the confusion is further exacerbated due to the fact that the term Coanda effect is sometimes used to explicitly refer to the mechanism underlying AGJD (Scherer et al, 2001;Erath and Plesniak, 2006a,b), whereas in other studies, it is used synonymously with the appearance of AGJD (Neubauer et al, 2007;Becker et al, 2009) itself. Furthermore, whereas some studies use this term to describe AGJD inside the glottis (Scherer et al, 2001;Erath and Plesniak, 2006a,b), others use it in conjunction with AGJD in the supraglottal flow (Neubauer et al, 2007;Becker et al, 2009).…”

“…Vortex strength is typically overpredicted in 2D models and this could have a noticeable effect on AGJD. It should be noted, however, that experiments (which include these latter 3D effects) have noted different degrees of AGJD (Erath and Plesniak, 2006a,b;Neubauer et al, 2007;Becker et al, 2009) and therefore the introduction of 3D effects does not seem to necessarily eliminate the occurrence of AGJD. Thus, the current 2D model is still expected to provide insights that would be useful for realistic glottal flows.…”

“…Furthermore, whereas some studies use this term to describe AGJD inside the glottis (Scherer et al, 2001;Erath and Plesniak, 2006a,b), others use it in conjunction with AGJD in the supraglottal flow (Neubauer et al, 2007;Becker et al, 2009). It should be noted that glottal jets are first unsteady, and second, they exhaust into a flow volume with preexisting finite magnitude asymmetric flow perturbations.…”

An experimental study of the glottal jet

“…The paper provides detailed data on jet core velocity, jet inclination angle, and also on the flow separation point, however only qualitatively. The paper of Becker et al [9] is focused on elucidation of the mechanisms of sound production in the larynx. The authors used a synthetic life-sized selfoscillating vocal fold model.…”

Assessment of local vocal fold deformation characteristics in an in vitro static tensile test

“…1 Both the geometry and the biomechanical tissue properties of the vocal folds influence voice quality, glottal airflow, 2 and the fundamental frequency of vibration. 3 In general, dysphonias based on morphological alterations yield a disturbed acoustic voice signal (e.g., hoarseness) and can be easily detected in endoscopic examinations.…”