Comparison of a fiber-gel finite element model of vocal fold vibration to a transversely isotropic stiffness model.

A fiber-gel vocal fold model is compared to a transversely isotropic stiffness model in terms of normal mode vibration. The fiber-gel finite element model (FG-FEM) consists of a series of gel slices, each with a two-dimensional finite element mesh, in a plane transverse to the tissue fibers. The gel slices are coupled with fibers under tension in the anterior-posterior dimension.

Time-Dependent Pressure and Flow Behavior of a Self-oscillating Laryngeal Model With Ventricular Folds.

Objective: The purpose of the study was to better understand the pressure-flow behavior of a self-oscillating vocal fold model at various stages of the glottal cycle.

Methods: An established self-oscillating vocal fold model was extended to include the false vocal folds (FVFs) and was used to study time-dependent pressure and velocity distributions through the larynx (including the true vocal folds [TVFs] and FVFs). Vocal fold vibration was modeled with a finite element method, laryngeal flow was simulated with the solution of unsteady Navier-Stokes equations, and the acoustics of the vocal tract was modeled with a wave reflection method.

Aerodynamic and acoustic effects of ventricular gap.

Purpose: Supraglottic compression is frequently observed in individuals with dysphonia. It is commonly interpreted as an indication of excessive circumlaryngeal muscular tension and ventricular medialization. The purpose of this study was to describe the aerodynamic and acoustic impact of varying ventricular medialization in a canine model.

Muscular anatomy of the human ventricular folds.

Objectives: Our purpose in this study was to better understand the muscular anatomy of the ventricular folds in order to help improve biomechanical modeling of phonation and to better understand the role of these muscles during phonatory and nonphonatory tasks.

Methods: Four human larynges were decalcified, sectioned coronally from posterior to anterior by a CryoJane tape transfer system, and stained with Masson's trichrome. The total and relative areas of muscles observed in each section were calculated and used for characterizing the muscle distribution within the ventricular folds.

A numerical and experimental investigation of the effect of false vocal fold geometry on glottal flow.

The false vocal folds are hypothesized to affect the laryngeal flow during phonation. This hypothesis is tested both computationally and experimentally using rigid models of the human larynges. The computations are performed using an incompressible Navier-Stokes solver with a second order, sharp, immersed-boundary formulation, while the experiments are carried out in a wind tunnel with physiologic speeds and dimensions.

Phonatory characteristics of the excised human larynx in comparison to other species.

Objective: The purpose of this study was to determine the conditions needed to elicit phonation from excised human larynges and the resultant range of phonations produced; compare that with similar information previously obtained from canine, pig, sheep, and cow; and relate those findings to previously reported information about viscoelastic properties of the vocal fold tissue (ie, stress-strain curves and Young's modulus).

Methods: Six human larynges of the geriatric group (age range, 70-89) were mounted on the bench without supraglottic structures, and phonation was achieved with the flow of heated and humidified air through the tracheal tube. Using various sutures to mimic the function of the laryngeal muscles, the larynges were put through a series of sustained oscillations with adduction as a control parameter.

On the acoustic effects of the supraglottic structures in excised larynges.

The acoustic effects of the supraglottic laryngeal structures (SGSs), including the false vocal folds (FVFs) laryngeal ventricle, and the epiglottis were investigated in an excised canine larynx model with and without these anatomical structures. The purpose of this study was to better understand the acoustic contributions of these structures to phonation. Canine larynges were prepared and mounted over a 3/4 in.

Measurement of vocal folds elastic properties for continuum modeling.

Objective: This study aimed to quantify the major elastic properties of human vocal fold's lamina propria, including longitudinal and transverse Young's modulus, shear modulus, and Poisson's ratio.

Methods: Samples were obtained from cadaveric human larynges that were snap frozen within 48 hours postmortem and kept at -82°F and thawed overnight in saline solution. Once the sample was tested in the longitudinal direction, two special brackets were glued to the side of each sample and the sample was mounted with brackets in the transverse direction.

Ventricular pressures in phonating excised larynges.

Pressure in the laryngeal ventricle was measured with a beveled needle connected to a pressure transducer in excised canine larynges. Air pressures within the ventricle were obtained for different adduction levels of the true vocal folds (TVFs), false vocal folds (FVFs), and subglottal pressures (Ps). Results indicated that the air pressures in the ventricle appear to be strongly related to the motion of the FVFs rather than to the effects of TVF vibration.

Measures of spectral slope using an excised larynx model.

Spectral measures of the glottal source were investigated using an excised canine larynx (CL) model for various aerodynamic and phonatory conditions. These measures included spectral harmonic difference H1-H2 and spectral slope that are highly correlated with voice quality but not reported in a systematic manner using an excised larynx model. It was hypothesized that the acoustic spectra of the glottal source were significantly influenced by the subglottal pressure, glottal adduction, and vocal fold elongation, as well as the resulting vibration pattern.

mRNA expression signatures of human skeletal muscle atrophy identify a natural compound that increases muscle mass.

Skeletal muscle atrophy is a common and debilitating condition that lacks a pharmacologic therapy. To develop a potential therapy, we identified 63 mRNAs that were regulated by fasting in both human and mouse muscle, and 29 mRNAs that were regulated by both fasting and spinal cord injury in human muscle. We used these two unbiased mRNA expression signatures of muscle atrophy to query the Connectivity Map, which singled out ursolic acid as a compound whose signature was opposite to those of atrophy-inducing stresses.

Vocal power and pressure-flow relationships in excised tiger larynges.

Despite the functional importance of loud, low-pitched vocalizations in big cats of the genus Panthera, little is known about the physics and physiology of the mechanisms producing such calls. We investigated laryngeal sound production in the laboratory using an excised-larynx setup combined with sound-level measurements and pressure-flow instrumentation. The larynges of five tigers (three Siberian or Amur, one generic non-pedigreed tiger with Bengal ancestry and one Sumatran), which had died of natural causes, were provided by Omaha's Henry Doorly Zoo over a five-year period.

Vocal fold elasticity in the pig, sheep, and cow larynges.

Elastic characteristics of the pig, sheep, and cow vocal folds were investigated through a series of in vitro experiments. Sample strips of the vocal-fold tissue were dissected from pig, sheep, and cow vocal folds and mounted inside a saline-filled ergometer chamber that was maintained at 37°C ± 1°C. Sinusoidal elongation was applied on the samples to obtain the passive force measurements.

Aerodynamic and acoustic effects of abrupt frequency changes in excised larynges.

Purpose: To determine the aerodynamic and acoustic effects due to a sudden change from chest to falsetto register or vice versa. It was hypothesized that the continuous change in subglottal pressure and flow rate alone (pressure-flow sweep [PFS]) can trigger a mode change in the canine larynx.

Method: Ten canine larynges were each mounted over a tapered tube that supplied pressurized, heated, and humidified air.

Phonatory characteristics of excised pig, sheep, and cow larynges.

The purpose of this study was to examine the phonatory characteristics of pig, sheep, and cow excised larynges and to find out which of these animal species is the best model for human phonation. Excised pig, sheep, and cow larynges were prepared and mounted over a tapered tube on the excised bench that supplied pressurized, heated, and humidified air in a manner similar to that for excised canine models. Each excised larynx was subjected to a series of pressure-flow experiments with adduction as major control parameter.

Glottal airflow resistance in excised pig, sheep, and cow larynges.

This study was to investigate glottal flow resistance in excised pig, sheep, and cow larynges during phonation at different oscillation ranges and to examine the relation of the glottal flow resistance to the laryngeal geometry and vocal fold vibration. Several pig, sheep, and cow larynges were prepared, mounted on an excised larynx bench, and set into oscillation with pressurized, heated, and humidified air. Glottal adduction was controlled by either using two-pronged probes to press the arytenoids together, or by passing a suture to simulate the lateral cricoarytenoid muscle action.

On pressure-frequency relations in the excised larynx.

The purpose of this study was to find relationships between subglottal pressure (P(s)) and fundamental frequency (F(0)) of phonation in excised larynx models. This included also the relation between F(0) and its rate of change with pressure (dFdP). Canine larynges were prepared and mounted over a tapered tube that supplied pressurized, heated, and humidified air.

Phonatory effects of supraglottic structures in excised canine larynges.

The aim of this study is to determine how phonation is affected by the presence and by alteration in the position of the supraglottic structures. The study used three excised canine larynges. A series of pressure-flow experiments were completed first on the excised larynx with false folds and epiglottis intact, then with the epiglottis removed, and finally with the false folds removed.

Aerodynamic and acoustic effects of false vocal folds and epiglottis in excised larynx models.

Objectives: The purpose of this study was to examine the aerodynamic and acoustic effects of the false vocal folds and the epiglottis on excised larynx phonation.

Methods: Several canine larynges were prepared and mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottal adduction was accomplished either by using two-pronged probes to press the arytenoids together or by passing a suture to simulate lateral cricoarytenoid muscle activation.

Sensitivity of elastic properties to measurement uncertainties in laryngeal muscles with implications for voice fundamental frequency prediction.

This paper discusses the effects of measurement uncertainties when calculating elastic moduli of laryngeal tissue. Small dimensions coupled with highly nonlinear elastic properties exacerbate the uncertainties. The sensitivity of both tangent and secant Young's Modulus was quantified in terms of the coefficient of variation, which depended on measurement of reference length and cross-sectional area.

Characterizing glottal jet turbulence.

Air pressure associated with airflow from the lungs drives the vocal folds into oscillation and allows the air to exit the glottis as a turbulent jet, even though laminar flow may enter the glottis from the trachea. The separation of the turbulence from the deterministic portion of the glottal jet was investigated in the excised canine larynx model. The present study is methodological in that the main goal was to examine three methods of obtaining reasonable representations of both the deterministic signal and the residual turbulence portion: (a) smoothing, (b) wavelet denoising, and (c) ensemble averaging.

Influence of vocal fold scarring on phonation: predictions from a finite element model.

Objectives: A systematic study of the influence of vocal fold scarring on phonation was conducted. In particular, phonatory variables such as fundamental frequency, oral acoustic intensity, and phonation threshold pressure (PTP) were investigated as a function of the size and position of the laryngeal scar.

Methods: By means of a finite element model of vocal fold vibration, the viscoelastic properties of both normal and scarred vocal fold mucosae were simulated on the basis of recent rheological data obtained from rabbit and canine models.

Active and passive properties of canine abduction/adduction laryngeal muscles.

Active and passive characteristics of the canine adductor- abductor muscles were investigated through a series of experiments conducted in vitro. Samples of canine posterior cricoarytenoid muscle (PCA), lateral cricoarytenoid muscle (LCA), and interarytenoid muscle (IA) were dissected from dog larynges excised a few minutes before death and kept in Krebs-Ringer solution at a temperature of 37 degrees C +/- 1 degree C and a pH of 7.4 +/- 0.

Flow separation in a computational oscillating vocal fold model.

A finite-volume computational model that solves the time-dependent glottal airflow within a forced-oscillation model of the glottis was employed to study glottal flow separation. Tracheal input velocity was independently controlled with a sinusoidally varying parabolic velocity profile. Control parameters included flow rate (Reynolds number), oscillation frequency and amplitude of the vocal folds, and the phase difference between the superior and inferior glottal margins.

A three-dimensional model of vocal fold abduction/adduction.

A three-dimensional biomechanical model of tissue deformation was developed to simulate dynamic vocal fold abduction and adduction. The model was made of 1721 nearly incompressible finite elements. The cricoarytenoid joint was modeled as a rocking-sliding motion, similar to two concentric cylinders.