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In speaking, shouting, and singing, vocal loudness is known to be regulated with lung pressure, but the degree to which vocal fold adduction and airway shape play a role in loudness control is less well known. When loudness is quantified in sones instead of sound pressure level (SPL), the regulatory mechanisms are even less obvious. Here it is shown computationally that loudness is insensitive to changes in SPL produced with variable adduction. A trade-off exists between a reduction in glottal flow amplitude and a flatter spectral slope. When the airway configuration is changed from a uniform tube to a "belt" or "call" shape, loudness can increase with a slight decrease in SPL. When the airway configuration is changed from a uniform tube to an operatic "ring" shape, loudness is increased with only a small increase in SPL.

The study addresses the benefit of tuning single harmonics with vocal tract resonances to increase vocal loudness. The loudness of theoretically constructed vocal sounds with variable levels of sound energy in the first, second, and third harmonics is computed on the basis of ISO standard 226:2003. In comparison to increased loudness with changes in overall spectral slope, it is shown that single harmonic tuning requires a greater range of SPL to produce a similar range of loudness. For example, a 10-40 dB increase in the level of a single harmonic produces less than two doublings of loudness, whereas a spectral slope change from -12 dB/octave to -3 dB/octave can produce a similar doubling of loudness with only a 5 dB SPL increase.

Self-sustained vocal fold vibration is possible with either or both of two mechanisms: (1) a mucosal wave propagating along the medial surface of the vocal folds and (2) a vocal tract that offers inertive reactance. A quantitative comparison shows the mucosal wave mechanism has a lower threshold pressure and a higher glottal efficiency, but the supraglottal inertance mechanism can assist in the oscillation and is effective in optimizing the two mechanisms. It is concluded that optimal parameters are a mucosal wave velocity on the order of 1 m/s and a diameter of the larynx canal (epilarynx tube) on the order of 0.8 cm.

The objective was to quantify the range of airflow resistance and oral pressure attainable with variation of length, diameter, and water immersion depth of tubes and straws.Pressure-flow equations for tubes, determined previously for variable tube geometries, were used to calculate oral pressure ranges. Human subjects were then recruited to use the variable tube geometries to produce oral pressures, which were quantified with commercial manometers.Nomograms for airflow resistances and oral pressures are plotted as a function of tube length, tube diameter, and water insertion depth.It is shown that tube diameters in the range of 2.5-3.0 mm with tube lengths of 10-40 cm produce oral pressures in the range of 10-40 cm H

The hypothesis tested was that the lung pressure required for multiphonic vocal sound sources (some combinations of true folds, false folds, aryepiglottis folds, tongue base, velum, lips) is the sum of all the individual threshold pressures. The approach was strictly computational. Fluid transport and wave propagation in the airways were produced by an abbreviated Navier–Stokes solution. Each of the sound sources was modeled with three narrow 0.2 cm sections having viscous and elastic wall properties that could oscillate in isolation. The length of the supraglottal vocal tract was 17.5 cm. The simulation was used to compute phonation threshold pressure, radiated power from the mouth, degree of aperiodicity, and glottal efficiency.

Any specific vowel sound that humans produce can be represented in terms of four perceptual features in addition to the vowel category. They are pitch, loudness, brightness, and roughness. Corresponding acoustic features chosen here are fundamental frequency (fo), sound pressure level (SPL), normalized spectral centroid (NSC), and approximate entropy (ApEn). In this study, thyroarytenoid (TA) and cricothyroid (CT) activations were varied computationally to study their relationship with these four specific acoustic features. Additionally, postural and material property variables such as vocal fold length (L) and fiber stress (&sigma, ) in the three vocal fold tissue layers were also calculated. A fiber-gel finite element model developed at National Center for Voice and Speech was used for this purpose. Muscle activation plots were generated to obtain the dependency of postural and acoustic features on TA and CT muscle activations. These relationships were compared against data obtained from previous in vivo human larynx studies and from canine laryngeal studies. General trends are that fo and SPL increase with CT activation, while NSC decreases when CT activation is raised above 20%. With TA activation, acoustic features have no uniform trends, except SPL increases uniformly with TA if there is a co-variation with CT activation. Trends for postural variables and material properties are also discussed in terms of activation levels.

OBJECTIVES/HYPOTHESIS Anterior (Wendler) glottoplasty has become a popular surgery for voice feminization. However, there has been some discrepancy between its theoretical pitch-raising potential and what is actually achievable, and downsides to shortening the glottis have not been fully explored. In addition, descriptions of the surgery are inconsistent in their treatment of the vocal ligament. This study aimed to determine 1) how fundamental frequency (fo ) is expected to vary with length of anterior glottic fixation, 2) the impact of glottic shortening on sound pressure level (SPL), and 3) the effect of including the ligament in fixation. STUDY DESIGN Computational simulation. METHODS Voice production was simulated in a fiber-gel finite element computational model using canonical male vocal fold geometry incorporating a three-layer vocal fold composition (superficial lamina propria, vocal ligament, and thyroarytenoid muscle). Progressive anterior glottic fixation (0, 1/8, 2/8, 3/8, etc. up to 7/8 of membranous vocal fold length) was simulated. Outcome measures were fo , SPL, and glottal flow waveforms. RESULTS fo increased from 110 Hz to 164 Hz when the anterior one-half vocal fold was fixed and continued to progressively rise with further fixation. SPL progressively decreased beyond 1/8 to 1/4 fixation. Inclusion of the vocal ligament in fixation did not further increase fo . Any fixation increased aperiodicity in the acoustic signal. CONCLUSIONS The optimal length of fixation is a compromise between pitch elevation and reduction in output acoustic power. The simulation also provided a potential explanation for vocal roughness that is sometimes noted after anterior glottoplasty. LEVEL OF EVIDENCE NA Laryngoscope, 131:1081-1087, 2021.

The purpose of this preliminary study was to investigate the feasibility of a tool to compare a severity index of nonlinear events and vocal self-rating over a long period of time. One hundred and ninety-seven phonations were analyzed to quantify the severity of instabilities in the voice attributed to nonlinear dynamic phenomena, including voice breaks, subharmonics, and frequency jumps. Instabilities were first counted; then a severity index was calculated for the instabilities in each phonation. The two quantities were compared to the subject's autoperceptual rating. Generally speaking, the measures derived from nonlinear dynamic analysis of the high-pitched, soft phonations followed the subject's own rating of inability to produce soft voice. These preliminary single subject results provide a foundation for future multi-subject studies to formulate acoustic and autoperceptual measures for the fatiguing effects of prolonged speaking in vocally demanding professions. However, given the number of observations, the results are still useful in showing general relationships. While future work should add additional subjects, a study providing preliminary evidence is useful before attempting to undertake a multi-subject study with complex analysis (i.e., individually selecting the nonlinear events) and with a long observation duration (days, weeks, and months) of subject.

Summary Objective To document and quantify vocal dose and student-singers' self-assessment during rehearsals for a contemporary musical theater production. Methods/Design Six student singers fastened the sensor from the KayPentax APM 3200 dosimeter to the lower neck to capture neck vibration data during their preparation for the musical Wonderland by Frank Wildhorn. Data were collected during 8-hour periods, at four different stages throughout the rehearsal process: beginning (music and choreography learning phase), middle (staging phase), and end (running the entire show/dress rehearsal phase), plus a post-production day once the production had concluded to establish a baseline vocal load. Students concurrently completed the EASE questionnaire 1 after each data collection day. Results The EASE score ( Appendix 1 ) and demographics/perceptual questionnaire ( Appendix 2 ) revealed that all subjects (three males and three females) found the singing role vocally and physically demanding but only two found the roles to be emotionally challenging. The musical score demanded a higher usage of chest register (judged perceptually) than mixed register from lead singers. All subjects’ maximum fundamental frequency range exceeded the pitch range required by the score. The mean vibration dose (distance dose) across all singers for rehearsal days was higher for females, 1,100,000 meters, than males, 900,000 meters, and the subjects’ self-ratings on the EASE were not correlated with the distance dose. Conclusions A review of Wonderland's score and perceptual judgment of the singers’ performances revealed extensive use of chest register, with belting and mix vocal strategies being the predominant stylistic choices. Students described the singing roles’ vocal and physical requirements as more challenging than the character's emotional components. This pilot study provides information on the vocal dose for lead and ensemble singers in rehearsal for a Contemporary Musical Theatre production. Singers and voice professionals may find dosimetry a valuable tool for monitoring the vocal dose during rehearsals and performances.

Steady airflow resistances in semi-occluded airways as well as acoustic impedances in vocalization are quantified from the lungs to the lips. For clinical and voice training applications, the primary focus is on two airway conditions, an oral semi-occlusion and a semi-occlusion above the vocal folds. Laryngeal airflow resistance is divided into glottal airflow resistance and epilaryngeal airway resistance. Maximum aerodynamic power is transferred to the vocal tract if the glottal airflow resistance is reduced while the epilaryngeal airway resistance is increased. A semi-occlusion at the lips helps to set up this condition. For the acoustic power transfer, the epilaryngeal airway also serves to match the impedance of the source to the impedance of the vocal tract.

Objective Most type 1 thyroplasty implants and some common injectable materials are mechanically stiff. Placing them close to the supple vocal fold mucosa can potentially dampen vibration and adversely impact phonation, yet this effect has not been systematically investigated. This study aims to examine the effect of implant depth on vocal fold vibration and vocal output. Study design Computational simulation. Methods Voice production was simulated with a fiber-gel finite element computational model that incorporates a three-layer vocal fold composition (superficial lamina propria, vocal ligament, thyroarytenoid muscle). Implants of various depths were simulated, with a "deeper" or more medial implant positioned closer to the vocal fold mucosa and replacing more muscle elements. Trajectories of surface and within-tissue nodal points during vibration were produced. Outcome measures were the trajectory radii, fundamental frequency (F0 ), sound pressure level (SPL), and smoothed cepstral peak prominence (CPPS) as a function of implant depth. Results Amplitude of vibration at the vocal fold medial surface was reduced by an implant depth of as little as 14% of the total transverse vocal fold depth. Increase in F0 and decrease in CPPS were noted beyond 30% to 40% implant depth, and SPL decreased beyond 40% to 60% implant depth. Conclusions Commonly used implants can dampen vibration "from a distance," ie, even without being immediately adjacent to vocal fold mucosa. Since implants are typically placed at depths examined in this study, stiff implants likely have a negative vocal impact in a subset of patients. Softer materials may be preferable, especially in bilateral medialization procedures. Level of evidence N/A Laryngoscope, 130:2192-2198, 2020.

The effective depth of vocal fold vibration is self-regulated and generally not known a priori in vocalization. In this study, the effective depth was quantified systematically under various phonatory conditions using a fiber-gel finite element vocal fold model. The horizontal and vertical excursions of each finite element nodal point trajectory were recorded to compute trajectory areas. The extent of vibration was then studied based on the variation of trajectory radii as a function of depth in several coronal sections along the anterior-posterior direction. The results suggested that the vocal fold nodal trajectory excursions decrease systematically as a function of depth but are affected by the layered structure of the vocal folds. The effective depth of vibration was found to range between 15 and 55% of the total anatomical depth across all phonatory conditions. The nodal trajectories from the current study were compared qualitatively with the results from excised human hemi-larynx experiments published in Döllinger and Berry [(2006). J. Voice. 20(3), 401-413]. An estimate of the effective mass of a one-mass vocal fold model was also computed based on the effective depth of vibration observed in this study under various phonatory conditions.

Purpose The purposes of this study are to introduce the concept of vocal priorities based on acoustic correlates, to develop an instrument to determine these vocal priorities, and to analyze the pattern of vocal priorities in patients with voice disorders. Method Questions probing the importance of 5 vocal attributes (vocal clarity, loudness, mean speaking pitch, pitch range, vocal endurance) were generated from consensus conference involving speech-language pathologists, laryngologists, and voice scientists, as well as patient feedback. The responses to the preliminary items from 213 subjects were subjected to exploratory factor analysis, which confirmed 4 of the predefined domains. The final instrument consisted of a 16-item Vocal Priority Questionnaire probing the relative importance of clarity, loudness, mean speaking pitch, and pitch range. Results The Vocal Priority Questionnaire had high reliability (Cronbach's α = .824) and good construct validity. A majority of the cohort (61%) ranked vocal clarity as their highest vocal priority, and 20%, 12%, and 7% ranked loudness, mean speaking pitch, and pitch range, respectively, as their highest priority. The frequencies of the highest ranked priorities did not differ by voice diagnosis or by sex. Considerable individual variation in vocal priorities existed within these large trends. Conclusions A patient's vocal priorities can be identified and taken into consideration in planning behavioral or surgical intervention for a voice disorder. Inclusion of vocal priorities in treatment planning empowers the patient in shared decision making, helps the clinician tailor treatment, and may also improve therapy compliance.

In this tribute article to D.G. Miller, we review some historical and recent contributions to understanding the myoelastic-aerodynamic (MEAD) theory of phonation and the related acoustic phenomena in subglottal and vocal tract. At the time of the formulation of MEAD by van den Berg in late 1950s, it was assumed that vocal fold oscillations are self-sustained thanks to increased subglottal pressure pushing the glottis to open and decreased subglottal pressure allowing the glottis to close. In vivo measurements of subglottal pressures during phonation invalidated these assumptions, however, and showed that at low fundamental frequencies subglottal pressure rather tends to reach a maximum value at the beginning of glottal closure and then exhibits damped oscillations. These events can be interpreted as transient acoustic resonance phenomena in the subglottal tract that are triggered by glottal closure. They are analogous to the transient acoustic phenomena seen in the vocal tract. Rather than subglottal pressure oscillations, a more efficient mechanism of transfer of aerodynamic energy to the vocal fold vibrations has been identified in the vertical phase differences (mucosal waves) making the glottal shape more convergent during glottis opening than during glottis closing. Along with other discoveries, these findings form the basis of our current understanding of MEAD.

This paper addresses the contributions of low-frequency postural laryngeal kinematics to frequency and amplitude modulations of the vocal output signal. A one-dimensional Navier–Stokes solution for fluid transport and wave propagation is used along with a laryngeal source model to simulate voice production. Vocal fold adduction and vertical laryngeal posture are modulated sinusoidally at 2–10 Hz with various amplitudes to approximate kinematic phenomena observed with MRI during production of vocal vibrato and voice tremor. The acoustic modulations are quantified in terms of formant (resonance) and fundamental frequency shifts in the radiated output signal from the mouth. Postural oscillation of the larynx is a common kinematic component of vocal tremor, although less documented during production of vibrato.

Objective This investigation addressed the desirable source–airway interaction obtained with vocalization through a semi-occlusion at the mouth. The semi-occlusion was a flow-resistant tube of varying length and diameter. Method The methodology was strictly computational. Airway shapes resembling those obtained from magnetic resonance or computed tomography imaging were stylized. Supraglottal and subglottal acoustic impedances were calculated, from which inertagrams were plotted over a frequency range of 0–4000 Hz. The inertagrams predict which harmonics are likely to be strengthened. Results The combination of epilaryngeal airway narrowing and lengthening, a pharyngeal expansion, and an oral narrowing behind the tube produce the best overall inertagram for pitch glide exercises. This configuration supports harmonics of the source evenly over a range of 300–4000 Hz. Conclusions For clinical applications, theory predicts that the length of a tube or straw does not matter if the inner diameter is on the order of 3 mm or less. For wider open-ended tubes, greater length can compensate for the wider diameter for the beneficial inertance effect, but the desired steady pressure in the airways for vocal fold posturing cannot be maintained.

While the novel coronavirus outbreak has profoundly altered health care systems across the globe, it has also affected similar change and devastation on the social, educational, and cultural communities upon which many rely, including communities of choral singers, solo performers, conductors, voice teachers, and the professionals that collaborate with them. Even as citizens of the most heavily impacted countries took to their balconies to serenade first responders and health care workers, singers of most genres who typically perform in ensembles have been told to not carry on their beloved practice. This message, promoted by the lay media and by early reports of “super-spreading” of the virus at choral events in the United States and abroad,1 , 2 has been reinforced by expert and nonexpert opinion regarding the transmissibility of SARS-CoV-2 through droplets and aerosols, the generation of respiratory particles when singing, and concern about the interpersonal interactions that routinely accompany vocal performance, both in groups and in one-on-one teaching situations. Unfortunately, there is a paucity of data about both how SARS-CoV-2 is transmitted by singing and how to bring communities of singers back together safely. The data available about disease spread through vocalization, most of which preceded the current pandemic, address primarily transmission of disease through droplets and aerosols and are specific neither to this virus nor to singing.3, 4, 5, 6 Specifically, there is a lack of data addressing how to congregate and sing safely in choral environments such as churches, concert halls and practice spaces, as well as stages, theatres and other venues. In addition, protective measures such as safest distancing between singers, wearing masks or other personal protective equipment (PPE), using larger rehearsal or performance spaces, reducing the number of singers inside a certain enclosed space, reducing the duration of rehearsals or performances, and using real time air and surface cleaning methods such as increased ventilation, UV-C light and HEPA filtration specific to a singing environment among other topics have not been studied well enough to provide evidence on which to base advice to the singing community. Opinion on these matters is plentiful and often divergent. A recent webinar with a panel of experts in the world of voice care and singing left the audience with the message, “There is no safe way for singers to rehearse together until there is a COVID-19 vaccine and a 95% effective treatment in place.”7 , 8 Although, this may ultimately prove to be accurate, evidence-based practice (defined as an approach to health that integrates scientific research, patient preferences and values, and clinical expertise to make the best recommendations possible) does not allow for such a definitive conclusion to be made at this time.9 It must be understood, that these recommendations and decisions are made not only on what scientific information is available but on intuition and unsystematic experience that is often biased and inaccurate. We do not understand all the risks posed by COVID 19 to ourselves, friends, family and colleagues, who wish to resume educational, performance, communal and congregational singing safely. Evidence-based practice demands that we critically evaluate our current state of knowledge to come up with the best possible information to disseminate. In this article, we review the information that exists relating to singing and COVID-19. This paper is intended to provide guidance based on what we know: the best available data, analyzed and scrutinized by a panel of experts in the medical, behavioral and basic science world of voice care, of whom many are professional singers, choir directors or teachers of singing. While it may not be able to afford any definitive answers, this work will offer suggestions of best practices for those singing groups that are willing to mitigate risk knowing that the risk cannot be brought to zero. Finally, this report will hopefully stimulate the larger voice research community to study the emerging consensus on safe resumption of singing and pursue scientific understanding of COVID-19.

Objective This investigation addresses the loudness variations in sones achievable with spectral slope variations (higher harmonic energy) in human vocalization and compares it to the sound pressure level (SPL) variations typically reported in the voice range profile (VRP). Method The primary methodology was computational. The ISO standard 226 was used to convert SPL values to sones for a 125- to 1000-Hz range of fundamental frequency and a –3 dB/octave to –12 dB/octave range of spectral slope. In addition, a retrospective analysis of human subjects' VRPs was conducted, and the experimental results were compared to the theoretical results. Results A very small range of SPL variation (less than 5 dB) in the VRP can produce a large range of loudness. The sensitivity can be on the order of 4 sones per dB SPL change. Conclusion For vocalization in the modal register, loudness variation is not well described by SPL change in dB, especially at high fundamental frequencies where the SPL range in the VRP becomes very small but sizeable loudness variations are still possible.

Long-distance vocal communication by birds and mammals, including humans, is facilitated largely by radiation efficiency from the mouth or beak. Here, this efficiency is defined and quantified. It depends on frequency content of vocalization, mouth opening, head and upper body geometry, and directionality. Each of these factors is described mathematically with a piston-in-a-sphere model. While this model is considered a classic, never before has the high frequency solution been applied in detail to vocalization. Results indicate that frequency content in the 1–50 kHz range can be radiated with nearly 100% efficiency if a reactance peak in the radiation impedance is utilized with adjustments of head size, mouth opening, and beam direction. Without these adjustments, radiation efficiency is generally below 1%, especially in human speech where a high fundamental frequency is a disadvantage for intelligibility. Thus, two distinct modes of vocal communication are identified, (1) short range with optimized information transfer and (2) long range with maximum efficiency for release of acoustic power.

The fluid-structure interaction and energy transfer from respiratory airflow to self-sustained vocal fold oscillation continues to be a topic of interest in vocal fold research. Vocal fold vibration is driven by pressures on the vocal fold surface, which are determined by the shape of the glottis and the contact between vocal folds. Characterization of three-dimensional glottal shapes and contact patterns can lead to increased understanding of normal and abnormal physiology of the voice, as well as to development of improved vocal fold models, but a large inventory of shapes has not been directly studied previously. This study aimed to take an initial step toward characterizing vocal fold contact patterns systematically. Vocal fold motion and contact was modeled based on normal mode vibration, as it has been shown that vocal fold vibration can be almost entirely described by only the few lowest order vibrational modes. Symmetric and asymmetric combinations of the four lowest normal modes of vibration were superimposed on left and right vocal fold medial surfaces, for each of three prephonatory glottal configurations, according to a surface wave approach. Contact patterns were generated from the interaction of modal shapes at 16 normalized phases during the vibratory cycle. Eight major contact patterns were identified and characterized by the shape of the flow channel, with the following descriptors assigned: convergent, divergent, convergent-divergent, uniform, split, merged, island, and multichannel. Each of the contact patterns and its variation are described, and future work and applications are discussed.

The definition of vocology is re-stated and its existence as a discipline for the study of all forms of vocalization across species is rationalized. A brief historical sketch is given regarding the...

Based on the assumption that individual sound intensities of singers are incoherent and add linearly to produce a combined choir intensity, a model of a voice range profile of a choir is produced. It is shown that this model predicts six distinct levels of choir dynamics (pp p mp mf f ff) over two octaves of fundamental frequency in a choir section. The levels are 3-6 dB apart, depending on the individual voice range profiles of the singers. Overall choir size has no effect on dynamic range, unless the size is varied dynamically by not all singers singing all the time. For a non-homogeneousn group of singers, a few loud voices dominate ff if everyone sings, while pp is not achieved effectively without suppressing all voices that cannot sing soft. Furthermore, the dynamic range can be significantly limited when choral blend for loudness is imposed on a non-homogeneous choir.

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. No vibrational displacement in the fiber-length direction is allowed, resulting in a plane strain state. This is consistent with the assumption of transverse displacement of a simple string, offering a wide range of natural frequencies (well into the kHz region) with variable tension. For low frequencies, the results compare favorably with the natural frequencies of a transversely isotropic elastic stiffness model (TISM) in which the shear modulus in the longitudinal plane is used to approximate the effect of fiber tension. For high frequencies, however, the natural frequencies do not approach the string mode frequencies unless plane strain is imposed on the TISM model. The simplifying assumption of plane strain, as well as the use of analytical closed-form shape functions, allow for substantial savings in computational time, which is important in clinical and exploratory applications of the FG-FEM model.

Summary Purpose Speech has been hailed as unique to human evolution. Although the inventory of distinct sounds producible with vocal tract articulators is a great advantage in human oral communication, it is argued here that the larynx as a sound source in speech is limited in its range and capability because a low fundamental frequency is ideal for phonemic intelligibility and source-filter independence. Method Four existing data sets were combined to make an argument regarding exclusive use of the larynx for speech: (1) range of fundamental frequency, (2) laryngeal muscle activation, (3) vocal fold length in relation to sarcomere length of the major laryngeal muscles, and (4) vocal fold morphological development. Results Limited data support the notion that speech tends to produce a contracture of the larynx. The morphological design of the human vocal folds, like that of primates and other mammals, appears to be optimized for vocal communication over distances for which higher fundamental frequency, higher intensity, and fewer unvoiced segments are used. Conclusion The positive message is that raising one's voice to call, shout, or sing, or executing pitch glides to stretch the vocal folds, can counteract this trend toward a contracted state.

The tissues of the body are routinely subjected to various forms of mechanical vibration, the frequency, amplitude, and duration of which can contribute both positively and negatively to human health. The vocal cords, which are in close proximity to the thyroid, may also supply the thyroid with important mechanical signals that modulate hormone production via mechanical vibrations from phonation. In order to explore the possibility that vibrational stimulation from vocalization can enhance thyroid epithelial cell function, FRTL-5 rat thyroid cells were subjected to either chemical stimulation with thyroid stimulating hormone (TSH), mechanical stimulation with physiological vibrations, or a combination of the two, all in a well-characterized, torsional rheometer-bioreactor. The FRTL-5 cells responded to mechanical stimulation with significantly (p, Highlights • Thyroid epithelial cells responded to mechanical vibrations similar to those from vocalization. • This response was equivalent or greater compared to chemical stimulation. • The combination of mechanical and chemical stimulation was synergistic. • It may be possible to influence thyroid function with mechanical vibrations.

The unique avian vocal organ, the syrinx, is located at the caudal end of the trachea. Although a larynx is also present at the opposite end, birds phonate only with the syrinx. Why only birds evolved a novel sound source at this location remains unknown, and hypotheses about its origin are largely untested. Here, we test the hypothesis that the syrinx constitutes a biomechanical advantage for sound production over the larynx with combined theoretical and experimental approaches. We investigated whether the position of a sound source within the respiratory tract affects acoustic features of the vocal output, including fundamental frequency and efficiency of conversion from aerodynamic energy to sound. Theoretical data and measurements in three bird species suggest that sound frequency is influenced by the interaction between sound source and vocal tract. A physical model and a computational simulation also indicate that a sound source in a syringeal position produces sound with greater efficiency. Interestingly, the interactions between sound source and vocal tract differed between species, suggesting that the syringeal sound source is optimized for its position in the respiratory tract. These results provide compelling evidence that strong selective pressures for high vocal efficiency may have been a major driving force in the evolution of the syrinx. The longer trachea of birds compared to other tetrapods made them likely predisposed for the evolution of a syrinx. A long vocal tract downstream from the sound source improves efficiency by facilitating the tuning between fundamental frequency and the first vocal tract resonance., Author summary The larynx is an important valve in the respiratory system of all air-breathing vertebrates that is located at the upper end of the trachea. In some amphibians, in nonavian reptiles, and in mammals, it has also assumed the function of a vocal organ. In contrast, birds have evolved a new and unique vocal organ, the syrinx, which is located at the lower end of the trachea. The selective forces that underlie the evolution of the syrinx as a novel organ have remained unclear. Among all air-breathing vertebrates, birds have the longest necks, and long necks require a long trachea. With a vocal organ at the base of the trachea, this long tube can act as vocal tract resonator and, therefore, can improve the conversion of aerodynamic energy into acoustic energy if fundamental frequency and a resonance frequency are matched. Here, we conducted experiments with simplified physical models, with real birds and a computational simulation in order to investigate the effect of the two different positions of a sound source within the respiratory tract. We find that sound is produced with greater efficiency by a sound source in syrinx position and that favorable interactions between sound source and vocal tract occur with syringeal position. The data provide support for the hypothesis that a selective pressure for high vocal efficiency may have contributed to the evolution of the syrinx in its unique location within the air tract.

Summary Objective This study examined the identification of emergency calling across distance without electronic assistance, as in the event of an electric grid black-out or being stranded in the wilderness. Methods Fifteen participants were callers and forty-one participants were recorders. Ten callers underwent an hour-long training in how to produce vocally healthy loud phonation, as well as, yodeled calls. Outdoors, the callers individually called out a set of single and multisyllable words, either yodeled or nonyodeled. Recorders and sound level meters were placed at four distances from the caller and were asked to select the called word as part of a closed-set identification task. Results Distances greater than 100 m had significantly reduced call identification. Caller sex did not yield statistically significant differences in call identification at any distance. Participation in training only yielded a statistically significant difference in call identification at 170 m. For distances greater than 25 m, multisyllabic words were significantly better identified than single syllable words. Nonyodeled calls had a higher score by a statistically significant amount for ranges above 50 m than yodeled calls. Yodeled calls were found to have a greater sound level than nonyodeled calls at greater distances. The study results were consistent with the inverse square law. Conclusions Even a small amount of training can provide improvement in identification at long distances. Multisyllable words provide better identification than single syllable identification at distances beyond 25 m. Future research is recommended, focusing particularly on the amount of training necessary to improve identification and environmental effects on identification.

Mechanical stimulation of cell cultures has been shown be an effective means of enhancing ECM production. ECM produced from vocal fold fibroblast cultures has the potential for therapeutic use for vocal fold repair. However, current bioreactor designs generally fail to produce physiological relevant frequency and strain values. Here we present an approach for using commercial oscillatory rheometers and an elastic ring bilayer system to produce physiologically relevant strain values at frequencies in the range of 20 – 100HZ. We demonstrate the ability to target specific strain and frequency values by manipulating system parameters, and also show that it is possible to maintain high oscillatory strains for extended periods of time. Such a system could be used to mechanically stimulate cell cultures contained within gel carrier systems and has the potential to be extended to other applications requiring high strains at low frequencies.

Objectives/Hypothesis To test the hypothesis that subligamental cordectomy produces superior acoustic outcome than subepithelial cordectomy for early (T1–2) glottic cancer that requires complete removal of the superficial lamina propria but does not involve the vocal ligament. Study Design Computer simulation. Methods A computational tool for vocal fold surgical planning and simulation (the National Center for Voice and Speech Phonosurgery Optimizer-Simulator) was used to evaluate the acoustic output of alternative vocal fold morphologies. Four morphologies were simulated: normal, subepithelial cordectomy, subligamental cordectomy, and transligamental cordectomy (partial ligament resection). The primary outcome measure was the range of fundamental frequency (F0) and sound pressure level (SPL). A more restricted F0-SPL range was considered less favorable because of reduced acoustic possibilities given the same range of driving subglottic pressure and identical vocal fold posturing. Results Subligamental cordectomy generated solutions covering an F0-SPL range 82% of normal for a rectangular vocal fold. In contrast, transligamental and subepithelial cordectomies produced significantly smaller F0-SPL ranges, 57% and 19% of normal, respectively. Conclusion This study illustrates the use of the Phonosurgery Optimizer-Simulator to test a specific hypothesis regarding the merits of two surgical alternatives. These simulation results provide theoretical support for vocal ligament excision with maximum muscle preservation when superficial lamina propria resection is necessary but the vocal ligament can be spared on oncological grounds. The resection of more tissue may paradoxically allow the eventual recovery of a better speaking voice, assuming glottal width is restored. Application of this conclusion to surgical practice will require confirmatory clinical data. Level of Evidence N/A. Laryngoscope, 125:1892–1899, 2015

Summary Source-filter interaction is a phenomenon in which acoustic airway pressures influence the glottal airflow at the source (level 1) and the vibration pattern of the vocal folds (level 2). This interaction is most significant when dominant source harmonics are near airway resonances. The influence of acoustic airway pressures on vocal fold vibration (level 2) was studied systematically by changing the supraglottal vocal tract length in human subjects with tube extensions. The subjects were asked to perform fundamental frequency (fo) glides while phonating through tubes of various lengths. An algorithm was developed using the quasi-open quotient extracted from the electroglottograph. Regions of sudden vocal fold vibration pattern change due to source-filter interaction were inferred from contact area changes. The algorithm correctly identified 89% of male and 84.8% of female quantal changes in contact pattern associated with interactions between source harmonics and formants during ascending glides. During the descending glides, the algorithm correctly identified 84% of male and 81.1% of female quantal changes in contact pattern. These results are in comparison with those obtained from the fo-based algorithm (Maxfield et al).

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.