Phonation Onset Pressure Research Articles

Sensitivity of Phonation Onset Pressure to Vocal Fold Stiffness Distribution.

Phonation onset is characterized by the unstable growth of vocal fold (VF) vibrations that ultimately results in self-sustained oscillation and the production of modal voice. Motivated by histological studies, much research has focused on the role of the layered structure of the vocal folds in influencing phonation onset, wherein the outer "cover" layer is relatively soft and the inner "body" layer is relatively stiff. Recent research, however, suggests that the body-cover (BC) structure over-simplifies actual stiffness distributions by neglecting important spatial variations, such as inferior-superior (IS) and anterior-posterior gradients and smooth transitions in stiffness from one histological layer to another. Herein, we explore sensitivity of phonation onset to stiffness gradients and smoothness. By assuming no a priori stiffness distribution and considering a second-order Taylor series sensitivity analysis of phonation onset pressure with respect to stiffness, we find two general smooth stiffness distributions most strongly influence onset pressure: a smooth stiffness containing aspects of BC differences and IS gradients in the cover, which plays a role in minimizing onset pressure, and uniform increases in stiffness, which raise onset pressure and frequency. While the smooth stiffness change contains aspects qualitatively similar to layered BC distributions used in computational studies, smooth transitions in stiffness result in higher sensitivity of onset pressure than discrete layering. These two general stiffness distributions also provide a simple, low-dimensional, interpretation of how complex variations in VF stiffness affect onset pressure, enabling refined exploration of the effects of stiffness distributions on phonation onset.

Reproducibility and Aging of Different Silicone Vocal Folds Models.

In this study, silicone vocal fold models with different geometries were manufactured using the common silicone brand EcoFlex 00-30 with typical oil mixing ratios. However, the proportions of oil typically used are higher than the manufacturer's recommended limit, in order to attain the softness of human vocal folds. This additional oil causes direct effects on the silicone, such as shrinkage, stickiness, evaporation, embrittlement, and uneven vulcanization. This study investigated the impact of these effects on the oscillation characteristics of the silicone vocal fold models and how they change over time. The goal was to examine the comparability of produced silicone vocal fold models and the results obtained from experiments performed with these models. For the manufactured models, the phonation onset pressure, offset pressure, mean volume velocity, pulmonary power, fundamental frequency, and measures of the glottal area waveform were collected over a period of up to 8 weeks. The results showed that the data for the models were highly scattered. Furthermore, over time, the phonation onset/offset pressures increased, leading to failure to oscillate for some models, and the glottal area waveform also changed. In conclusion, when working with over-thinned silicone vocal fold models, their characteristics depend strongly on the time of measurement. Therefore, it is recommended to carefully consider the effects of oil-oversaturation and timing of measurements when using silicone vocal fold models in experiments.

Effects of Arytenoid Adduction Suture Position on Voice Production and Quality.

Arytenoid adduction (AA) is performed to treat unilateral vocal fold paralysis with a large posterior glottal gap. However, the voice effects of AA suture position remain unclear. This study aimed to evaluate voice production and quality as a function of AA suture position on the thyroid ala in a neuromuscularly intact in vivo larynx. Animal model. Unilateral recurrent laryngeal nerve and vagal paralysis were modeled in two canines. AA suture position was varied across five equidistant positions on the anterior inferior thyroid ala, from a paramedian position anteriorly to the oblique line posteriorly. Phonation was performed over 8 × 8 graded level combinations of recurrent and superior laryngeal nerve stimulation per suture position. The primary outcome was percent successful phonatory conditions. Secondary outcomes included fundamental frequency (F0), phonation onset pressure (PTP), cepstral peak prominence (CPP), and laryngeal posture. Anterior suture positions resulted in a greater percentage of successful phonatory conditions compared to posterior sutures. Suture position 2, located at the anterior inferior thyroid ala, resulted in the highest percentage of successful phonatory conditions, lowest PTP, and lower muscle activation levels to achieve higher CPP. Posterior sutures resulted in wider glottal gap and more effective F0 and vocal fold strain increase with cricothyroid muscle contraction, but with fewer successful phonatory conditions and higher PTP. Trends were consistent across both paralysis types. AA suture placed in the anterior inferior thyroid ala resulted in the best acoustic, aerodynamic, and voice quality outcomes. This study provides scientific evidence for maintaining current clinical practice. NA Laryngoscope, 131:846-852, 2021.

Contributions of rapid neuromuscular transmission to the fine control of acoustic parameters of birdsong.

It is largely unknown how fine motor control of acoustic parameters is achieved in vocal organs. Subtle manipulation of syringeal muscle function was used to test how active motor control influences acoustic parameters. Slowed activation kinetics of muscles reduced frequency modulation and, unexpectedly, caused a distinct decrease in sound amplitude and increase in phonation onset pressure. These results show that active control enhances the efficiency of energy conversion in the syrinx.

Interactions of subglottal pressure and neuromuscular activation on fundamental frequency and intensity.

Fundamental frequency (F0) and intensity sound pressure level (SPL) of voice are controlled by intrinsic laryngeal muscle (ILM) activation and subglottal pressure (Psub). Their interactions were investigated. In an in vivo canine model, the thyroarytenoid (TA), lateral cricoarytenoid/interarytenoid (LCA/IA), and cricothyroid (CT) muscles were independently activated from threshold to maximal contraction by neuromuscular stimulation in various combinations, whereas airflow was increased to phonation onset pressure and beyond. The resultant acoustic output was analyzed for effects of Psub on vibratory stability, F0, and SPL. Muscle activation plots and vocal range profiles by individual ILM activation states were analyzed. Cricothyroid activation increased phonation onset F0, but vibration was less stable in high CT conditions and displayed vibratory mode change. In addition, a decrease in F0 with increased Psub was observed in high CT conditions. Intensity increased with Psub in all conditions, but the slope was greater at high CT, low TA/LCA/IA activations. Lateral cricoarytenoid/interarytenoid activation improved vocal efficiency. To maintain same F0 with increasing SPL (messa di voce), TA activation was decreased and LCA/IA activation was increased. The same F0 and SPL could be achieved with a variety of ILM activation combinations. Cricothyroid is primarily required for increasing F0, whereas TA can increase or decrease F0 and SPL. Lateral cricoarytenoid/interarytenoid activation likely maintains vocal fold adduction during increased Psub and improves vocal efficiency. This study also demonstrates laryngeal motor equivalence, the ability of the larynx to achieve the same target F0 and SPL with multiple combinations of ILM activation. N/A. Laryngoscope, 126:1123-1130, 2016.

Differential roles for the thyroarytenoid and lateral cricoarytenoid muscles in phonation.

Laryngeal adductor muscle dysfunction is a common cause of voice disorders. Reconstitution of adductor muscle function is often the target of therapy, but the effects of these muscles on voice production remain to be fully understood. This study investigated the differential roles of thyroarytenoid (TA) and lateral cricoarytenoid (LCA) muscles on voice production. Basic science study using an in vivo canine model of phonation. The TA and LCA muscle nerve branches were stimulated to obtain seven graded levels of muscle activation, from threshold to maximal contraction. The effects of LCA muscle activation alone, TA muscle activation alone, and combined TA and LCA muscle activation on phonation onset parameters were investigated. Phonatory posture, phonation onset type, fundamental frequency (F0), phonation onset pressure, and airflow were evaluated. LCA muscle activation closed the posterior glottis, but the midmembranous gap remained. TA muscle activation closed the membranous glottis, but the posterior gap remained. Complete glottal closure was obtained only with combined TA and LCA muscle activation. Phonation onset with the LCA muscle alone was characterized by multiple modes (soft, aperiodic, periodic), whereas with the TA muscle alone it was abrupt and periodic but had significant baseline noise. Combined muscle activation led to elimination of baseline noise with stable abrupt periodic onset of phonation. Combined muscle activation was also necessary for F0 variation. The LCA muscle assisted the TA muscle in increasing subglottal pressure while concurrently reducing phonation onset airflow. The TA muscle is necessary for F0 variation, stable onset phonation, and increased subglottal pressure, but needs the LCA muscle for optimal effectiveness and to reduce airflow requirements with increased activation. NA.

Neuromuscular control of fundamental frequency and glottal posture at phonation onset.

The laryngeal neuromuscular mechanisms for modulating glottal posture and fundamental frequency are of interest in understanding normal laryngeal physiology and treating vocal pathology. The intrinsic laryngeal muscles in an in vivo canine model were electrically activated in a graded fashion to investigate their effects on onset frequency, phonation onset pressure, vocal fold strain, and glottal distance at the vocal processes. Muscle activation plots for these laryngeal parameters were evaluated for the interaction of following pairs of muscle activation conditions: (1) cricothyroid (CT) versus all laryngeal adductors (TA/LCA/IA), (2) CT versus LCA/IA, (3) CT versus thyroarytenoid (TA) and, (4) TA versus LCA/IA (LCA: lateral cricoarytenoid muscle, IA: interarytenoid). Increases in onset frequency and strain were primarily affected by CT activation. Onset pressure correlated with activation of all adductors in activation condition 1, but primarily with CT activation in conditions 2 and 3. TA and CT were antagonistic for strain. LCA/IA activation primarily closed the cartilaginous glottis while TA activation closed the mid-membranous glottis.

Frequency response of synthetic vocal fold models with linear and nonlinear material properties.

The purpose of this study was to create synthetic vocal fold models with nonlinear stress-strain properties and to investigate the effect of linear versus nonlinear material properties on fundamental frequency (F0) during anterior-posterior stretching. Three materially linear and 3 materially nonlinear models were created and stretched up to 10 mm in 1-mm increments. Phonation onset pressure (Pon) and F0 at Pon were recorded for each length. Measurements were repeated as the models were relaxed in 1-mm increments back to their resting lengths, and tensile tests were conducted to determine the stress-strain responses of linear versus nonlinear models. Nonlinear models demonstrated a more substantial frequency response than did linear models and a more predictable pattern of F0 increase with respect to increasing length (although range was inconsistent across models). Pon generally increased with increasing vocal fold length for nonlinear models, whereas for linear models, Pon decreased with increasing length. Nonlinear synthetic models appear to more accurately represent the human vocal folds than do linear models, especially with respect to F0 response.

Effects of asymmetric vocal fold activation on phonation.

The effects of asymmetric vocal fold activation on phonation were studied using an in vivo canine model and graded neuromuscular stimulation of the recurrent laryngeal nerve (RLN). One RLN was stimulated at 21 levels of graded stimulation, from threshold activity to maximal contraction, at three levels of contralateral vocal fold contraction (low, medium, and high). Phonation onset pressure (Pth) was recorded at each condition. The effects of airflow and cricothyroid (CT) muscle activation were studied by varying airflow and CT activation levels. Pth remained relatively constant over nearly all conditions while the level of graded stimulation needed to reach Pth varied. Increasing airflow and higher level of contralateral vocal fold activation allowed Pth to be reached at lower levels of graded stimulation, while activation of CT muscles had the opposite effect. At maximal CT activation, Pth was reached only at high levels of contralateral vocal fold activation but Pth was doubled. Results show that in vocal fold paresis/paralysis, phonation onset can be achieved by increasing either airflow or activation level of the normal vocal fold, and that CT activation increases the phonatory effort. These results provide further insights into the compensatory mechanisms required for phonation in these common laryngeal pathologies.

Influence of vocal fold stiffness on phonation characteristics at onset in a body-cover vocal fold model

The influence of the body and cover stiffnesses on phonation onset and the resulting vibration pattern was investigated in a body-cover continuum model of the vocal folds. An eigenvalue analysis was performed to obtained phonation onset characteristics. The analysis showed that, with increasing body-cover stiffness ratio, both the phonation threshold pressure and frequency (normalized by the Young's modulus and wave speed of the cover layer, respectively) first increased rapidly and then gradually approached a plateau. For a given glottal resting opening, a soft vocal fold body led to a larger prephonatory glottal opening, which had an negative effect on phonation onset pressure, and for certain vocal fold geometries, led to a local minimum in the phonation threshold pressure as a function of the body stiffness. Although the phonation threshold pressure was low for a vocal fold configuration with both a soft cover and a soft body, the vocal fold vibration at onset exhibited a significant whole-body vertical motion and a low sound production efficiency, and therefore it may not be desirable for voice production. For a large body-cover stiffness ratio, this vertical motion was suppressed and vibration was restricted to the cover layer and the medial surface, resulting in a more effective flow modulation and a better sound production efficiency.