Eric J. Hunter

Suitability of Dysphonia Measurements for Telemonitoring of Parkinson's Disease

In this paper, we present an assessment of the practical value of existing traditional and nonstandard measures for discriminating healthy people from people with Parkinsons disease (PD) by detecting dysphonia. We introduce a new measure of dysphonia, pitch period entropy (PPE), which is robust to many uncontrollable confounding effects including noisy acoustic environments and normal, healthy variations in voice frequency. We collected sustained phonations from 31 people, 23 with PD. We then selected ten highly uncorrelated measures, and an exhaustive search of all possible combinations of these measures finds four that in combination lead to overall correct classification performance of 91.4%, using a kernel support vector machine. In conclusion, we find that nonstandard methods in combination with traditional harmonics-to-noise ratios are best able to separate healthy from PD subjects. The selected nonstandard methods are robust to many uncontrollable variations in acoustic environment and individual subjects, and are thus well suited to telemonitoring applications.

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. The vocal ligament and the thyroarytenoid muscles fiber characteristics were implemented as a fiber-gel composite made of an isotropic ground substance imbedded with fibers. These fibers had contractile and/or passive nonlinear stress-strain characteristics. The verification of the model was made by comparing the range and speed of motion to published vocal fold kinematic data. The model simulated abduction to a maximum glottal angle of about 31 degrees. Using the posterior-cricoarytenoid muscle, the model produced an angular abduction speed of 405 degrees per second. The system mechanics seemed to favor abduction over adduction in both peak speed and response time, even when all intrinsic muscle properties were kept identical. The model also verified the notion that the vocalis and muscularis portions of the thyroarytenoid muscle play significantly different roles in posturing, with the muscularis portion having the larger effect on arytenoid movement. Other insights into the mechanisms of abduction/adduction were given.

Voicing and silence periods in daily and weekly vocalizations of teachers

The National Center for Voice and Speech (NCVS) data bank on voice dosimetry was used to study the distributions of continuous voicing periods and silence periods in 31 teachers over the duration of two weeks. Recordings were made during all awake hours of the day. Voicing periods were grouped into half decades, ranging from 0.0316 to 0.10 s for the shortest periods of phonation to 31.6-100 s for the longest periods of phonation. Silence periods were grouped into similar half decades, but ranged up to periods of several hours. On average, the teachers had 1800 occurrences of voicing (onset followed by offset) per hour at work and 1200 occurrences per hour while not at work. Voicing occurred 23% of the total time at work, dropping to 13% during off-work hours and 12% on weekends. The greatest accumulation of voicing occurred in the 0.316-1.0 s voicing periods, whereas the greatest accumulation of silence occurred in the 3-10 s silence periods. The study begins to lay the groundwork for understanding vocal fatigue in terms of repetitive motion and collision of tissue, as well as recovery from such mechanical stress.

Quantifying vocal fatigue recovery: Dynamic vocal recovery trajectories after a vocal loading exercise

Objectives We quantified the recovery of voice following a 2-hour vocal loading exercise (oral reading). Methods Eighty-six adult participants tracked their voice recovery using short vocal tasks and perceptual ratings after an initial vocal loading exercise and for the following 2 days. Results Short-term recovery was apparent, with 90% recovery within 4 to 6 hours and full recovery at 12 to 18 hours. Recovery was shown to be similar to a dermal wound healing trajectory. Conclusions The new recovery trajectory highlighted by the vocal loading exercise in the current study is called a vocal recovery trajectory. By comparing vocal fatigue to dermal wound healing, this trajectory is parallel to a chronic wound healing trajectory (as opposed to an acute wound healing trajectory). This parallel suggests that vocal fatigue from the daily use of the voice could be treated as a chronic wound, with the healing and repair mechanisms in a state of constant repair. In addition, there is likely a vocal fatigue threshold at which point the level of tissue damage would shift the chronic healing trajectory to an acute healing trajectory.

Gender differences affecting vocal health of women in vocally demanding careers.

Abstract Studies suggest that occupational voice users have a greater incidence of vocal issues than the general population. Women have been found to experience vocal health problems more frequently than men, regardless of their occupation. Traditionally, it has been assumed that differences in the laryngeal system are the cause of this disproportion. Nevertheless, it is valuable to identify other potential gender distinctions which may make women more vulnerable to voice disorders. A search of the literature was conducted for gender-specific characteristics which might impact the vocal health of women. This search can be used by health care practitioners to help female patients avoid serious vocal health injuries, as well as to treat better those women who already suffer from such vocal health issues.

Cervids with different vocal behavior demonstrate different viscoelastic properties of their vocal folds.

The authors test the hypothesis that vocal fold morphology and biomechanical properties covary with species‐specific vocal function. They investigate mule deer (Odocoileus hemionus) vocal folds, building on, and extending data on a related cervid, the Rocky Mountain elk (Cervus elaphus nelsoni). The mule deer, in contrast to the elk, is a species with relatively little vocal activity in adult animals. Mule deer and elk vocal folds show the typical three components of the mammalian vocal fold (epithelium, lamina propria and thyroarytenoid muscle). The vocal fold epithelium and the lamina propria were investigated in two sets of tensile tests. First, creep rupture tests demonstrated that ultimate stress in mule deer lamina propria is of the same magnitude as in elk. Second, cyclic loading tests revealed similar elastic moduli for the vocal fold epithelium in mule deer and elk. The elastic modulus of the lamina propria is also similar between the two species in the low‐strain region, but differs at strains larger than 0.3. Sex differences in the stress–strain response, which have been reported for elk and human vocal folds, were not found for mule deer vocal folds. The laminae propriae in mule deer and elk vocal folds are comparatively large. In general, a thick and uniformly stiff lamina propria does not self‐oscillate well, even when high subglottic pressure is applied. If the less stiff vocal fold seen in elk is associated with a differentiated lamina propria it would allow the vocal fold to vibrate at high tension and high subglottic pressure. The results of this study support the hypothesis that viscoelastic properties of vocal folds varies with function and vocal behavior. J. Morphol., 2010.

Comparison of human, canine, and ovine laryngeal dimensions

Geometric measurement of the laryngeal skeleton is a fundamental step in laryngeal studies, especially in biomechanical modeling. Traditionally, canine larynges have been used as models of the human larynx because of their similarity in size and gross structure, but the search continues for an alternative model because of the diminishing availability of the canine species for research in the United States. In this report, a revised method for defining and labeling laryngeal framework parameters is proposed. Ovine laryngeal cartilages were measured, and the measurements were compared to those of human and canine cartilages previously reported in the literature. The ovine cricoid, thyroid, and arytenoid cartilages were significantly different from the human and canine cartilages. Also, the lack of a definite border between the true and false vocal folds revealed that the ovine model may not always be suitable for a direct comparison to the human larynx in phonation.

A two-dimensional biomechanical model of vocal fold posturing

The forces and torques governing effective two-dimensional (2D) translation and rotation of the laryngeal cartilages (cricoid, thyroid, and arytenoids) are quantified on the basis of more complex three-dimensional movement. The motions between these cartilages define the elongation and adduction (collectively referred to as posturing) of the vocal folds. Activations of the five intrinsic laryngeal muscles, the cricothyroid, thyroarytenoid, lateral cricoarytenoid, posterior cricoarytenoid, and interarytenoid are programmed as inputs, in isolation and in combination, to produce the dynamics of 2D posturing. Parameters for the muscles are maximum active stress, passive stress, activation time, contraction time, and maximum shortening velocity. The model accepts measured electromyographic signals as inputs. A repeated adductory-abductory gesture in the form /hi-hi-hi-hi-hi/ is modeled with electromyographic inputs. Movement and acoustic outputs are compared between simulation and measurement.

Toward a consensus on symbolic notation of harmonics, resonances, and formants in vocalization

Toward a consensus on symbolic notation of harmonics, resonances, and formants in vocalization

Intraoral pressures produced by thirteen semi-occluded vocal tract gestures

Abstract The use of semi-occluded vocal tract (SOVT) exercises as habilitative and rehabilitative tools has grown substantially in the past two decades. As the use of these exercises has grown, so too has the number of variations of the phonatory gestures used to create oral semi-occlusions. While much of the research on SOVT exercises to this point has been conducted using straw phonation, there has been little discussion or investigation regarding how other phonatory gestures that are considered to be SOVT compare to one another. The current study sought to measure the intraoral pressure produced by 13 phonatory gestures generally thought of as oral semi-occlusions. Twenty subjects (10 male, 10 female) produced three tokens of each gesture, and intraoral pressure was recorded via a thin, flexible-cannula pressure transducer. Pressures ranged between 0.1 and 1.0 kPa, but varied significantly between gestures and between subjects.