VOCAL DAMPING: HISTORY, PHYSIOLOGY, AND NEW PERSPECTIVES
The history of vocal damping
Damping is traditionally described as a particular glottic phonatory behavior, in which the posterior part of the vocal folds is tightly adducted and vibration occurs only in an anterior portion of variable length. Historically, this phenomenon has attracted great interest among researchers in the field of voice physiology.
Figure 1. Examples of vocal damping configurations in male (left) and female (right) glottis
The first description of this peculiar glottic configuration dates back to 1886, when the physician and laryngologist Morell Mackenzie defined it as stop-closure. In his book The Hygiene of the Vocal Organs: A Practical Handbook for Singers and Speakers, he wrote:
“There is another kind of closure, however, which is much more significant, and that is stopclosure; by this term I understand a condition of the glottis in which its mem-branous lips are not simply in contact, but pressed together so tightly for a greater or less portion of their length as to prevent each other from vibrating at that part. This is done either by the edge of one lip overlapping that of the other, or by both cords being forced against each other in such a way as to turn their edges upwards. This mechanism is brought into use whenever the head-notes are employed by women or the falsetto by men” [1].
A few years earlier, physiologist and singing teacher Emil Behnke, together with ENT surgeon Lennox Browne, had analyzed vocal registers through in vivo images of the larynx. In his book The Mechanism of the Human Voice (1881), Behnke wrote:
“There are, broadly speaking, three registers in the human voice, and the mechanisms are plainly visible, as follows: (1) During the lowest series of tones the vocal ligaments vibrate in their entire thickness. (2) During the next series of tones the vocal ligaments vibrate only with their thin inner edges. (3) During the highest series of tones a portion of the vocal chink is firmly closed, and only a small part of the vocal ligaments vibrates” [2].
The third vocal register described by Behnke is similar to Mackenzie’s stop-closure, representing a glottic behavior in which a portion of the vocal folds is strongly adducted and vibration occurs only in the remaining anterior part. Like stop-closure, Behnke’s glottic behavior was also observed in high-pitched vocalizations. In 1942, laryngologist Joel Pressman—pioneer of high-speed laryngeal imaging—was the first to photograph this specific glottic behavior and to define it as damping or dampening. Unsurprisingly, it later became universally known as the Pressman damping factor. In his 1955 article Physiology of the Larynx, Pressman wrote:
“The technique of laryngeal damping consists in the appropriate segment of one vocal cord coming into direct and forceful contact with the corresponding segment of the other, and retaining this position during the duration of the production of the tone. These approximated segments of the cords have been damped, one by the other, and are thus prevented from vibrating regardless of the pressure of the expiratory blast. The functionally foreshortened portions of the cord anterior to the damped segments remain free to vibrate and, because they are foreshortened without changes in tension or thickness, vibrate more rapidly with a resultant increase in pitch. […] As higher tones are pro-duced in a gradually ascending scale, the length of segment damped by the other becomes longer and the vibrating portion correspondingly shorter, the damping process ex-tending anteriorly as a continuous approximation of in-creasing length. Finally so great a length of the cords is approximated that the chink of the glottis consists of nothing more than a very tiny orifice located anteriorly. […] In the transition from the mechanism of parallel cords to damping there is sometimes noticeable a change in the quality of the voice and the transition is known as a ‘break’” [3].
It is clear that Pressman not only described damping as a phonatory behavior in which the vocal folds vibrate in a “shortened” configuration, but also hypothesized that by varying the length of the vibrating portion, pitch could be modified—exactly as in string instruments. William Vennard later explained this analogy in his book Singing: The Mechanism and the Technic:
“These words [see: damping/dampening] apply to holding a string so that it cannot vibrate, and they implied a comparison with the finger of a violinist moving along the string in order to raise the pitch. It was assumed that somehow the glottis was pressed together at the back end, and that as the pitch rose, the damping was increased until finally only a small part of the ‘strings’ was allowed to vibrate”. [4]
In 1977, phonetician J.C. Catford also described four possible glottic configurations during phonation: complete, anterior, posterior, and ventricular glottis. The anterior configuration was described as follows:
“The arytenoid cartilages are apparently clamped tightly together and only the front, ligamental part of the glottis actively participates in phonation”[5].
Two years earlier, in 1975, Gould had analyzed possible relationships between vocal training, lung volumes, and the Pressman damping factor, suggesting that increased respiratory capacity—typical of trained singers—might be a crucial factor in improving damping during the production of high notes in head voice [6].
Surprisingly, few further studies were conducted on damping in the following years. One of the last detailed historical analyses is found in James Stark’s book Bel Canto: A History of Vocal Pedagogy (1999). In the section Modern views of glottal settings, the author states:
“Garcia ‘pinched glottis’, Mackenzie’s ‘stop-closure’, Pressman’s ‘damping factor’, Catford’s ‘anterior phonation’ and Lever’s ‘tense voice’ are all descriptions of a shortened glottis which results from a strong glottal closure. While shortened glottis seems to be a well accepted theory among some researchers, more laboratory research into glottal closure is needed in order to produce the objective data that would better describe the exact nature of the shortened glottis”[7].
In 2007, Roubeau et al. proposed the modern classification of vibratory mechanisms—M0, M1, M2, and M3. In that paper, the authors did not explicitly refer to glottic behaviors compatible with damping, though they analyzed various vibratory patterns across registers from endoscopic, acoustic, and electroglottographic perspectives [8].
The physiology of damping: what do we know?
Based on the historical-scientific literature, damping can be considered a well-documented phonatory behavior, with distinctive characteristics, traditionally described as an anterior-vibration glottic configuration occurring most typically in the high-pitched range, in both men and women.
But what are the precise physiological features of damping, and how does it relate to the vibratory mechanisms traditionally described?
Historically, damping has been associated with countertenors and sopranists, who can produce extremely high and brilliant pitches precisely thanks to a shortening of the vibrating portion of the glottis.
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Nevertheless, perceptually “damped” voices are increasingly heard today, particularly in the context of contemporary commercial music. Typically, a damping emission is characterized by a high-pitched sound, timbrically “full,” very bright, and penetrating.
Male voices most commonly use damping emissions to reach tonal ranges that are typically female.
Female voices, on the other hand, tend to use damping emissions in the super-high register:
Preliminary studies by Fussi and Fantini, based on flow glottograms and electroglottographic data, suggested that damping might be a variant of M2 and attributable to the falsetto domain in terms of underlying mechanism [9].
However, more recent multidimensional investigations—including videolaryngostroboscopy, electroacoustic analysis, and electroglottography—have shown that while the most common manifestation of damping indeed occurs in M2, glottic behaviors attributable to damping are also clearly identifiable within other vibratory mechanisms, both M3 and M1. It is known, for example, that whistle register (M3) can be obtained with either “full” glottic configurations (involving the entire length of the folds) or with “damping” configurations. At the same time, even high-pitched M1 emissions can sometimes be observed with “damping” glottic behaviors.
These observations open the way to interesting physiological insights and pedagogical implications. Some recently observed features of damping could even justify its classification as an independent mechanism, according to the definitions proposed by Roubeau and colleagues.
From a biomechanical point of view, damping is likely achieved through predominant activation of the intrinsic muscles involved in adduction of the cartilaginous component of the folds (lateral cricoarytenoid and interarytenoid muscles), with a probable reduced requirement of cricothyroid muscle activation, especially in M2d emissions. This would result in a shortened glottis, less tilted, yet highly efficient in vibration.
Recent observations and research perspectives
A recently published study in the Journal of Voice [10] examined the voices of 10 professional singers (musical theater performers), analyzing emission physiology in relation to known mechanisms across different frequency ranges. Although the sample size was small, the observations were thorough and the findings particularly interesting, especially regarding manifestations of damping across vocal registers.
This preliminary study identified damping behaviors (indicated for convenience with a lowercase d) not only in M2 emissions (M2d), but also in M3 (M3d, both male and female voices) and in M1 (M1d, observed only in certain male voices during high-pitched phonations). It also revealed typical register-change patterns in transitions from M1 to M2d, from M2 to M2d, and from M2d to M3 during ascending and descending glissandos (Figure 2).
Figure 2. Example of an ascending glissando analyzed with a multidimensional approach (electroacoustic, electroglottographic, and videolaryngostroboscopic analysis) showing a clear mechanism shift between M2–M2d and M2d–M3.
Moreover, typical electroacoustic and electroglottographic register-shift patterns were also detected in the transition between M2 and M2d on a sustained vowel at the same pitch (Figure 3).
Figura3. Example of a passaggio between M2d-M2 on a sustained note.
Preliminary data further suggested that, at least for M2d, there exists a specific range of intensity and frequency, supporting the identity and mechanical robustness of this phonatory behavior and opening the door to studies analyzing the detailed phonetographic characteristics of damped emissions.
Finally, in three singers, the study highlighted not only a “static” damping configuration of the glottis, but the actual dynamic functioning of damping as historically described by Pressman. Indeed, in a baritone, a mezzo, and a soprano, it was observed that the ratio between vibrating portion and fold length progressively decreased as pitch increased, and vice versa—exactly as happens with string instruments (Figure 4).
Figure 4. Example of dynamic manifestations of damping: as pitch rises, the vibrating glottic portion gradually decreases..
In light of these findings, extremely interesting physiological perspectives emerge: damping could be considered either a mechanism in its own right (a physiological manifestation that cuts across known vibratory mechanisms) or a sub-mechanism (a variant of some major glottic mechanisms). What is certain is that a deeper understanding of damping could provide valuable pedagogical insights, especially regarding its role in passaggio management, in mix voice, and in its relationship with falsetto, chest voice, and whistle.
Conclusions
In conclusion, damping should not be regarded as a mere physiological curiosity. It may represent a strategy to produce high and brilliant notes with less effort and greater efficiency, especially in vocal styles such as opera or musical theater.
Given the evidence so far, the fact that not all singers can activate it with the same ease suggests that individual anatomical factors, in addition to technical-vocal skills, also play a role.
For singing teachers and speech-language pathologists, a deep understanding of damping could provide new insights and physiological perspectives in both pedagogy and vocal rehabilitation. For singers, damping represents an additional expressive and technical resource that can be explored and integrated into their vocal development.
References
[1] Meckenzie Morell. The Hygiene of the Vocal Organs: A Practical Handbook for Singers and Speakers. London, UK: Macmillan and Co; 1886.
[2] Behnke E. The Mechanism of the Human Voice. 12 ed London, UK: J. Curwen & Sons; 1880.
[3] Pressman JJ, Kelenen G. Physiology of the larynx. Physiol Rev. 1955;35:506–554.
[4] William Vennard. Singing: The Mechanism and the Technic. New York, NY: C. Fischer; 1967.
[5] Catford JC. Fundamental Problems in Phonetics. Edinburgh, UK: Edinburgh University Press; 1977:280.
[6] Gould WJ. The effect of voice training on lung volume in singers and the possible relationship to the damping factor of Pressman. J Res Sing. 1977;1:3–15.
[7] Stark James. Bel Canto: A History of Vocal Pedagogy. Toronto, ON: University of Toronto Press; 1999.
[8] Roubeau B, Henrich N, Castellengo M. Laryngeal vibratory me-chanisms: the notion of vocal register revisited. J Voice. 2009;23:425–438. https://doi.org/10.1016/j.jvoice.2007.10.014.
[9] Fussi F, Fantini M. Stop-closure falsetto: M1 o M2?. Atti del 13 Congresso “La Voce Artistica”, 18-21 novembre 2021, Ravenna.
[10] Fantini M. The Physiology of Vocal Damping: Historical Overview and Descriptive Insights in Professional Singers. J Voice. 2024 Sep 2:S0892-1997(24)00265-0. doi: 10.1016/j.jvoice.2024.08.015. Epub ahead of print. PMID: 39227274.
Quest’opera è distribuita con Licenza Creative Commons Attribuzione – Non commerciale – Non opere derivate 4.0 Internazionale
Medico Chirurgo, Specialista in Otorinolaringoiatria, esperto in Vocologia professionale ed artistica, Deglutologia, Fonochirurgia.
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