A theoretical study of the effects of various laryngeal configurations on the acoustics of phonation

Abstract

Simulation of glottal volume flow and vocal fold tissue movement was accomplished by numerical solution of a time-dependent boundary value problem, in which nonuniform, orthotropic, linear, incompressible vocal fold tissue media were surrounded by irregularly shaped boundaries, which were either fixed or subject to aerodynamic stresses. Spatial nonuniformity of the tissues was of the layered type, including a mucosal layer, a ligamental layer, and muscular layers. Orthotropy was required to stabilized the vocal folds longitudinally and to accomodate large variations in muscular stress. Incompressibility and vertical motions at the golttis played an important role in producing and sustaining phonation. A nominal configuration for male fundamental speaking pitches was selected, and the regulation of fundamental frequency, intensity, average volume flow, and vocal efficiency was investigated in terms of variations around this nominal configuration. Parameters which were varied consisted of geometrical factors such as length, thickness, and depth, factors for shaping the glottis, as well as tissue elasticities, tissue viscosities, and subglottal pressure. Since nonlinear stress-strain properties were not included, subglottal pressure did not produce a pronounced effect upon fundamental frequency under these somewhat edealized conditions F0 rasing correlated strongly with increased tension in the ligament, and somewhat with increasing tension in the vocalis. F0 lowering correlated with increase in vocal fold length when the tensions were held constant, but not with increase in vocal fold thickness. Vocal intensity and efficiency are shown to have local maxima as the configurational parameters are varied one at a time. It appears that oral acoustic power output and vocal efficiency can be maximized by proper adjustments of longitudinal tension of nonmuscular (mucosal and ligamental) tissue layers in relation to muscular layers. Quantitative verification of the "body-cover" theory is therefore suggested, and several further implications with regard to control of the human larynx are considered.

An overview of the physiology, physics and modeling of the sound source for vowels.

“…This model allows for simulation of the vibrational pattern of the vocal folds in both the coronal and traverse planes. A further step up in complexity came with a continuum mechanics model [21] and a more recent finiteelement model [22] both of which provide a precise physiological and mechanical representation of the tissue layers of the vocal folds without lumping large anatomical regions into a few mass elements. Their large number of degrees of freedom allows for detailed study of the complex vibratory pattern observed in human vocal folds.…”

Influence and interactions of laryngeal adductors and cricothyroid muscles on fundamental frequency and glottal posture control

“…Due to the technical challenges of in vivo experiments, mostly theoretical studies have been used to understand the influence of neuromuscular activation and laryngeal posture on phonation dynamics. For example, Titze and Talkin (1979) found that fundamental frequency (F0) of phonation was primarily controlled by longitudinal tension (associated with glottal length) and that trans-glottal pressure was less effective. Actively controlled muscular contraction appears to provide the necessary flexibility for the glottis to allow a broad F0 range and the many varieties of phonation (Titze, 1994;Titze and Talkin, 1979).…”

“…For example, Titze and Talkin (1979) found that fundamental frequency (F0) of phonation was primarily controlled by longitudinal tension (associated with glottal length) and that trans-glottal pressure was less effective. Actively controlled muscular contraction appears to provide the necessary flexibility for the glottis to allow a broad F0 range and the many varieties of phonation (Titze, 1994;Titze and Talkin, 1979). However, the interactions of ILMs and their influence on phonatory posture and resulting dynamics remain poorly understood and have not been systematically investigated in experimental in vivo models.…”

Las bases psico-biológicas de la comunicación intersubjetiva en el arte

“…Mauleón y Gurlekian (2001), compararon la articulación de consonantes oclusivas en el habla y en el canto, y encontraron que a diferencia del habla en el canto persistía la vibración glótica durante la fase de oclusión de estas consonantes. La articulación es entonces, uno de los medios técnicos de alto valor expresivo que el cantante maneja con sutileza y en forma significativamente diferenciada con respecto al habla, Más aún, dada la estrecha relación entre articulación y resonancia (Sundberg, 1974), existen aún variaciones más sutiles que el can-tante puede imponer al sonido, dependiendo de la configuración del tracto vocal inferior, por ejemplo, variando la altura relativa de la laringe puede conseguirse un timbre con más o menos armónicos graves, y una de las estrategias de que se vale para lograr esto es la forma en que realiza la inspiración previa al canto (Gramming et al, 1993;Watson y Hixon, 1985;Sundberg y Nordstöm, 1983, 1987Titze y Talkin, 1979). Pero, la utilización de este tipo de recursos vocales (variación en la posición de la laringe o el vibrato, o cambios articulatorios) está guiada generalmente por el uso "consciente" de mecanismos cuasi-reflejos que el cantante maneja generalmente de forma intuitiva, recurriendo a la estrategia de "pensar" o imaginar el color vocal deseado o la emoción afín a las características sonoras que desea.…”