Principal dimensions of voice production and their role in vocal expression.

How we produce and perceive voice is constrained by laryngeal physiology and biomechanics. Such constraints may present themselves as principal dimensions in the voice outcome space that are shared among speakers. This study attempts to identify such principal dimensions in the voice outcome space and the underlying laryngeal control mechanisms in a three-dimensional computational model of voice production.

Estimating subglottal pressure and vocal fold adduction from the produced voice in a single-subject study (L).

We previously reported a simulation-based neural network for estimating vocal fold properties and subglottal pressure from the produced voice. This study aims to validate this neural network in a single-human subject study. The results showed reasonable accuracy of the neural network in estimating the subglottal pressure in this particular human subject.

Estimation of vocal fold physiology from voice acoustics using machine learning.

The goal of this study is to estimate vocal fold geometry, stiffness, position, and subglottal pressure from voice acoustics, toward clinical and other voice technology applications. Unlike previous voice inversion research that often uses lumped-element models of phonation, this study explores the feasibility of voice inversion using data generated from a three-dimensional voice production model. Neural networks are trained to estimate vocal fold properties and subglottal pressure from voice features extracted from the simulation data.

Effect of changes in medial surface shape on voice production in excised human larynges.

Clinical intervention of glottal insufficiency often focuses on correcting glottal gap as visualized from above. In contrast, changes in medial surface shape due to intervention have received less attention. This study investigated how changes in medial surface shape affect voice production in excised human larynges, by locally medializing the medial surface at different longitudinal and vertical locations.

Structural constitutive modeling of the anisotropic mechanical properties of human vocal fold lamina propria.

The anisotropic mechanical properties of the vocal fold lamina propria play an important role in voice production and control. The goal of this study is to develop a constitutive model capable of predicting lamina propria elastic moduli along both the longitudinal and transverse directions under different conditions of vocal fold elongation, which can be used as input to reduced-order phonation models based on linear elasticity. A structurally-based constitutive model that links microstructural characteristics of the lamina propria to its macromechanical properties is proposed.

Impact of Subharmonic and Aperiodic Laryngeal Dynamics on the Phonatory Process Analyzed in Ex Vivo Rabbit Models.

Normal voice is characterized by periodic oscillations of the vocal folds. On the other hand, disordered voice dynamics (e.g.

Investigation of phonatory characteristics using ex vivo rabbit larynges.

Quantitative analysis of phonatory characteristics of rabbits has been widely neglected. However, preliminary studies established the rabbit larynx as a potential model of human phonation. This study reports quantitative data on phonation using ex vivo rabbit larynx models to achieve more insight into dependencies of three main components of the phonation process, including airflow, vocal fold dynamics, and the acoustic output.

Biaxial mechanical properties of human vocal fold cover under vocal fold elongation.

Mechanical properties of the human vocal fold cover layer were experimentally investigated in uniaxial and biaxial tensile tests. The results showed a coupling effect between the stress conditions along the anterior-posterior and transverse directions, with vocal fold elongation increasing vocal fold stiffness along both directions, thus allowing more efficient control of the fundamental frequency of voice through vocal fold elongation. This study also shows that vocal folds were nearly isotropic at resting conditions, thus a tendency to vibrate with incomplete glottal closure, but became increasingly anisotropic with increasing vocal fold elongation.

Laryngeal muscular control of vocal fold posturing: Numerical modeling and experimental validation.

A three-dimensional continuum model of vocal fold posturing was developed to investigate laryngeal muscular control of vocal fold geometry, stiffness, and tension, which are difficult to measure in live humans or in vivo models. This model was able to qualitatively reproduce in vivo experimental observations of laryngeal control of vocal fold posturing, despite the many simplifications which are necessary due to the lack of accurate data of laryngeal geometry and material properties. The results present a first comprehensive study of the co-variations between glottal width, vocal fold length, stiffness, tension at different conditions of individual, and combined laryngeal muscle activation.

Experimental validation of a three-dimensional reduced-order continuum model of phonation.

Due to the complex nature of the phonation process, a one-dimensional (1D) glottal flow description is often used in current phonation models. Although widely used in voice research, these 1D flow-based phonation models have not been rigorously validated against experiments. In this study, a 1D glottal flow model is coupled with a three-dimensional nonlinear continuum model of the vocal fold and its predictions are compared to physical model experiments.

Dynamic vocal fold parameters with changing adduction in ex-vivo hemilarynx experiments.

Ex-vivo hemilarynx experiments allow the visualization and quantification of three-dimensional dynamics of the medial vocal fold surface. For three excised human male larynges, the vibrational output, the glottal flow resistance, and the sound pressure during sustained phonation were analyzed as a function of vocal fold adduction for varying subglottal pressure. Empirical eigenfunctions, displacements, and velocities were investigated along the vocal fold surface.

Impact of Vocal Tract Resonance on the Perception of Voice Quality Changes Caused by Varying Vocal Fold Stiffness.

Experiments using animal and human larynx models are often conducted without a vocal tract. While it is often assumed that the absence of a vocal tract has only small effects on vocal fold vibration, it is not actually known how sound production and quality are affected. In this study, the validity of using data obtained in the absence of a vocal tract for voice perception studies was investigated.

A computational study of the effect of intraglottal vortex-induced negative pressure on vocal fold vibration.

Recent studies reported the formation of intraglottal vortices for medium and high subglottal pressures in excised-larynx experiments, and hypothesized that the suction force created by these vortices might affect vocal fold vibration. However, high subglottal pressures often lead to large vocal fold elastic recoil forces, and it is unclear if the vortex-induced suction force is large enough compared with the elastic recoil force to have noticeable effects on vocal fold vibration. In this study, the validity of this hypothesis was examined using a computational model.

Perceptual consequences of changes in epilaryngeal area and shape.

The influence of epilaryngeal area on glottal flow and the acoustic signal has been described [Titze, J. Acoust. Soc.

The glottaltopogram: a method of analyzing high-speed images of the vocal folds.

Laryngeal high-speed videoendoscopy is a state-of-the-art technique to examine physiological vibrational patterns of the vocal folds. With sampling rates of thousands of frames per second, high-speed videoendoscopy produces a large amount of data that is difficult to analyze subjectively. In order to visualize high-speed video in a straightforward and intuitive way, many methods have been proposed to condense the three-dimensional data into a few static images that preserve characteristics of the underlying vocal fold vibratory patterns.

Variability in the relationships among voice quality, harmonic amplitudes, open quotient, and glottal area waveform shape in sustained phonation.

Increases in open quotient are widely assumed to cause changes in the amplitude of the first harmonic relative to the second (H1*-H2*), which in turn correspond to increases in perceived vocal breathiness. Empirical support for these assumptions is rather limited, and reported relationships among these three descriptive levels have been variable. This study examined the empirical relationship among H1*-H2*, the glottal open quotient (OQ), and glottal area waveform skewness, measured synchronously from audio recordings and high-speed video images of the larynges of six phonetically knowledgeable, vocally healthy speakers who varied fundamental frequency and voice qualities quasi-orthogonally.

Perceptual interaction of the harmonic source and noise in voice.

Although the amount of inharmonic energy (noise) present in a human voice is an important determinant of vocal quality, little is known about the perceptual interaction between harmonic and inharmonic aspects of the voice source. This paper reports three experiments investigating this issue. Results indicate that perception of the harmonic slope and of noise levels are both influenced by complex interactions between the spectral shape and relative levels of harmonic and noise energy in the voice source.

Experiments on Analysing Voice Production: Excised (Human, Animal) and (Animal) Approaches.

Unlabelled: Experiments on human and on animal excised specimens as well as animal preparations are so far the most realistic approaches to simulate the process of human phonation. These experiments do not have the disadvantage of limited space within the neck and enable studies of the actual organ necessary for phonation, i.e.

Effects of native language on perception of voice quality.

Little is known about how listeners judge phonemic versus allophonic (or freely varying) versus post-lexical variations in voice quality, or about which acoustic attributes serve as perceptual cues in specific contexts. To address this issue, native speakers of Gujarati, Thai, and English discriminated among pairs of voices that differed only in the relative amplitudes of the first versus second harmonics (H1-H2). Results indicate that speakers of Gujarati (which contrasts H1-H2 phonemically) were more sensitive to changes than are speakers of Thai or English.

Perceptual sensitivity to first harmonic amplitude in the voice source.

Little is known about the perceptual importance of changes in the shape of the source spectrum, although many measures have been proposed and correlations with different vocal qualities (breathiness, roughness, nasality, strain...

When and why listeners disagree in voice quality assessment tasks.

Modeling sources of listener variability in voice quality assessment is the first step in developing reliable, valid protocols for measuring quality, and provides insight into the reasons that listeners disagree in their quality assessments. This study examined the adequacy of one such model by quantifying the contributions of four factors to interrater variability: instability of listeners' internal standards for different qualities, difficulties isolating individual attributes in voice patterns, scale resolution, and the magnitude of the attribute being measured. One hundred twenty listeners in six experiments assessed vocal quality in tasks that differed in scale resolution, in the presence/absence of comparison stimuli, and in the extent to which the comparison stimuli (if present) matched the target voices.

Measures of the glottal source spectrum.

Purpose: Many researchers have studied the acoustics, physiology, and perceptual characteristics of the voice source, but despite significant attention, it remains unclear which aspects of the source should be quantified and how measurements should be made. In this study, the authors examined the relationships among a number of existing measures of the glottal source spectrum, along with the association of these measures to overall spectral shapes and to glottal pulse shapes, to determine which measures of the source best capture information about the shapes of glottal pulses and glottal source spectra.

Method: Seventy-eight different measures of source spectral shapes were made on the voices of 70 speakers.

A quantitative study of the medial surface dynamics of an in vivo canine vocal fold during phonation.

Objectives/hypothesis: The purpose of this study was to measure the medial surface dynamics of a canine vocal fold during phonation. In particular, displacements, velocities, accelerations, and relative phase velocities of vocal fold fleshpoints were reported across the entire medial surface. Although the medial surface dynamics have a profound influence on voice production, such data are rare because of the inaccessibility of the vocal folds.

Perception of aperiodicity in pathological voice.

Although jitter, shimmer, and noise acoustically characterize all voice signals, their perceptual importance in naturally produced pathological voices has not been established psychoacoustically. To determine the role of these attributes in the perception of vocal quality, listeners were asked to adjust levels of jitter, shimmer, and the noise-to-signal ratio in a speech synthesizer, so that synthetic voices matched naturally produced tokens. Results showed that, although listeners agreed well in their judgments of the noise-to-signal ratio, they did not agree with one another in their chosen settings for jitter and shimmer.