Function of the vocal folds. Glottis
LARYNX- the initial cartilaginous section of the respiratory system in humans and terrestrial vertebrates between the pharynx and trachea, is involved in voice formation.
From the outside, its position is noticeable by the protrusion of the thyroid cartilage - Adam's apple ( Adam's apple) more developed in ♂.
Laryngeal cartilages:
- epiglottis,
- thyroid,
- cricoid,
- two arytenoids.
When swallowing, the epiglottis closes the entrance to the larynx.
From the arytenoids to the thyroid there are mucous folds - vocal cords (there are two pairs of them, and only the lower pair is involved in voice formation). They oscillate at a frequency of 80-10,000 vibrations/s. The shorter the vocal cords, the higher the voice and the more frequent the vibrations.
The ligaments close when talking, rub when screaming and become inflamed (alcohol, smoking).
Functions of the larynx:
1) breathing tube;
Stands calmly, breathes deeply, sings
Articulation- the work of the speech organs performed when pronouncing a particular sound; degree of clarity of pronunciation. Articulate speech sounds are formed in the oral and nasal cavities depending on the position of the tongue, lips, jaws and the distribution of sound flows.
Tonsils- organs of the lymphatic system in terrestrial vertebrates and humans, located in the mucous membrane of the oral cavity and pharynx. Participate in protecting the body from pathogenic microbes and in developing immunity.
TRACHEA
Trachea (windpipe)- part of the respiratory tract of vertebrates and humans, between the bronchi and larynx in front of the esophagus. Its length is 15 cm. The anterior wall consists of 18-20 hyaline half-rings connected by ligaments and muscles with the soft side facing the esophagus. The trachea is lined with ciliated epithelium, the vibrations of the cilia of which remove dust particles from the lungs into the pharynx. It divides into two bronchi - this is a bifurcation.
BRONCHI
Bronchi- tubular air-bearing branches of the trachea.
In 1741 Ferrein(Ferrein) was the first to conduct experiments on the dead larynx, which were later carefully checked by I. Muller. It turned out that only “in general” the number of vibrations of the vocal cords obeys the laws of string vibration, according to which doubling the number of vibrations of any string requires squaring the tension weight.
Muller cut vocal cord length, pressing them in different places with tweezers both under tension and in various relaxed states. It turned out that depending on the tension of the ligaments, either low or high sounds are obtained when both long and short ligaments function.
Great importance is attached vocal muscle activity(m. thyreo-arythenoideus s. vocalis). On a living larynx, the pitch of sound depends not on lengthening, but on contraction of the vocal cords, which is ensured by the activity of m. vocalis (V.S. Kantorovich). Shorter and more elastic vocal cords, other things being equal, provide an increase in sound, which corresponds to the physical concepts of a vibrating string. At the same time, thickening of the vocal cords leads to a decrease in sound.
When as you rise pitch tension of the vocal muscles(without thickening of the ligaments) becomes insufficient, the thyroid-cricoid muscles, which stretch (but not lengthen) the vocal cords, contribute to the increase in tone (M. I. Fomichev).
Vocal cord vibrations can be carried out not along their entire length, but only on a certain segment, due to which an increase in tone is achieved. This occurs due to contraction of the oblique and transverse fibers of the vocalis muscle and possibly the oblique and transverse muscles, the arytenoid cartilages, and the lateral cricoarytenoid muscle.
M. I. Fomichev believes that the position of the epiglottis has some influence on the pitch. At very low tones, the epiglottis is usually very depressed, and the vocal cords become vast during laryngoscopy. As you know, closed pipes produce a lower sound than open ones.
In singing, there is a distinction between chest and falsetto. sounds. Muzehold was able to use laryngostroboscopic photographs to trace individual slow movements of the vocal cords.
In chest voice, the cords appear as two thick tension rollers, tightly compressed with each other. The sound here is rich in overtones and their amplitude slowly decreases with increasing height, which gives the timbre a fullness character. The presence of chest resonance in the chest register is disputed by most researchers.
In falsetto, the ligaments appear flattened, strongly stretched and a gap is formed between them. Only the free edges of the true ligaments vibrate, moving upward and laterally. There is no complete interruption of air during falsetto. As the falsetto tone increases, the glottis shortens due to the complete closure of the ligaments in the posterior regions.
With a mixed sound, the ligaments vibrate approximately half their width.
The speech spectrum of sounds differs in strength, pitch and timbre.
The strength of the voice depends mainly on the amplitude (span) of vibrations of the voice.
vocal cords, and it, in turn, depends on the pressure of the exhaled stream
air, the degree of tension of the vocal folds. The more they fill
air into the lungs, the greater the force of exhalation, the louder the sound.
But in any case, the voice arising in the larynx has little power.
The resonator cavities of the extension play a major role in amplifying the voice.
tubes (pharynx, oral and nasal cavity, and paranasal sinuses), they are not
only amplify sounds, but also give the voice a certain timbre,
is the place where speech sounds are formed.
The pitch of the voice depends on the frequency of vibration of the vocal cords, which,
in turn, depends on the length, thickness, elasticity and
vocal cord tension. The longer the vocal cords, the thicker they are
and the less tense, the lower the sound of the voice.
Changing the pitch of the voice is achieved by reducing certain
laryngeal muscles. When pronouncing (or singing) low sounds, vocal cords
ki are stretched slightly. The cricothyroid muscle is not functional
only the vocal (thyroarytenoid) muscle contracts, which when
its contraction becomes thicker and thereby increases the thickness of the
loose fold.
To increase sound, the cricothyroid is included in its activity.
muscle that increases tension on the vocal cords. At its maximum
contraction, a further increase in the tension of the vocal cords becomes
impossible, and raising the voice is ensured by another mechanism -
shortening of the vibrating part of the vocal cords. This is achieved by reducing
the transverse arytenoid muscle, the arytenoid cartilages are tightly attached
press against each other, as a result of which the posterior ends of the vocal cords are not
may fluctuate. Only the anterior part of the vocal cords vibrates,
which, having shortened, like the strings of a violin pressed with a finger, begin to
produce a higher sound. To further raise the voice, start again
The tension on the already shortened vocal cords begins to increase. When
there comes a limit to the tension and shortening of the vibrating segments of the vocal
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ligaments, the falsetto mechanism comes into effect, the ligaments vibrate
only thin edges in the longitudinal direction.
Voice timbre. Besides pitch and strength, different people's voices vary
sound color or timbre. The vibration frequency of the vocal cords is trained
catches the pitch of the fundamental tone. Along with the main tone in the larynx, there is
additional tones or overtones also develop, among them there are sharply pronounced
overtones with large amplitudes, which are called formants.
The number and strength of the sound of overtones depend on individual characteristics.
the structure of the larynx, as well as the size and shape of the resonator cavities
parts of the extension tube (pharynx, oral cavity, nasal cavity). Defined
A different combination of overtones gives the voice an individual “color”, or
timbre, which allows you to distinguish and recognize people by voice. The timbre of the voice
Loveka is usually defined as “pleasant”, “melodic”, “metallic”
skiy", "deaf", "soft", etc.
In addition to the above factors, voice quality (pitch and timbre) is influenced by
influence the degree of dryness or excessive moisture of the ligaments and respiration -
body pathways, the degree of their individual elasticity, etc.
Voice range. Limits of possible voice changes in pitch, from
the lowest sound that an instrument or voice can make, to the lowest
th high are called range. Vocal ranges for different people
are different. A person's voice can vary in pitch by approximately
within two octaves. For normal conversational speech, 4–6 tones are sufficient.
In men, the vocal range averages from 80 to 580 Hz, in women
The voice range is from 170 to 1034 Hz.
Anatomical differences in the larynxes, especially in the length of the vocal cords,
affecting their oscillatory properties, lead to the separation of
bass, tenor, soprano, etc.
Men have three types of singing voices: tenor, baritone and bass.
− Tenor – high voice: the length of the vocal folds varies pre-
cases 18–22 mm, the number of vibrations per second is 122–580.
− Baritone – voice of medium height: length of vocal folds – 22–24
mm, number of vibrations 96–426 per second.
− Bass – low voice: length of vocal folds – 23–25 mm, no.
number of oscillations per second – 81–125.
For women there are: contralto, mezzo-soprano, soprano.
− Contralto – low voice: length of vocal folds 20–22 mm,
the number of their vibrations is 145–690 per second.
− Mezzo-soprano – voice of medium height: length of vocal folds
18–21 mm, number of vibrations 217–864 per second.
− Soprano (dramatic, lyric and coloratura) – high
voice: length of vocal folds 10–17 mm, number of vibrations
258–1,304 per second
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The vocal range of children is much smaller than that of adults. With age
the range of children's voices increases (almost the same for boys
and girls), covering approximately the following boundaries:
from 8 to 10 years – 320-512 Hz;
from 10 to 12 years – 290-580 Hz;
from 12 to 14 years – 256-680 Hz
Both boys and girls have treble and alto
singing voices: treble - high child's voice, alto - low voice.
The limited range of a child's voice must be taken into account when
selection of repertoire for children to perform during singing lessons and during children's
amateur performances.
Voice registers. Each range has several registers. Re-
hyster is a series of sounds that are similar in the mechanism of formation and character
sound. There are three voice registers: chest, head and mixed
(mixed).
The chest register got its name due to the fact that with it
zones the chest, the walls of which give a clearly noticeable vibration
tion. The chest voice is rich in overtones. In chest voice the ligaments are tight
close, oscillate with their entire mass in a direction perpendicular to
rated current of the air stream, i.e. in the transverse direction. To the chest region
stru refers to low tones of voice. Chest resonance informs sound
fullness and volume of sound.
The head register is characterized by a head resonance, which
can be detected during phonation in the form of vibration of the skull bones, putting
hand on the crown. A typical example of the head register is falsetto
voice. It is distinguished by its poverty of overtones. The head register is used
in the upper tones of the range
A mixed voice (mixed) is richer in overtones compared to
falsetto, but poorer than a chest voice. The glottis does not close
completely, the ligaments vibrate over a wider surface than with false
tse, and sometimes with its entire mass. The mixed tone includes the middle tones of the holo-
owl range.
In singing, all three registers of the voice are used, in colloquial speech (in
adults) – mostly mixed. In children before puberty,
Only the falsetto voice functions.
Sound attack. The figurative term “attack” denotes a method of bringing
activation of vocal cords that are at rest. The attack of sound is called
They sometimes “take” a sound, “attack”, “vocal beginning”. There are three
type of attacks: hard, soft, aspirated.
With a hard attack, the vocal cords close tightly before the sound begins,
then the exhaled air forcefully breaks through the closed voice
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a gap and causes vibration of the ligaments. A solid attack is characterized by the presence
which is at the very beginning of the sound of a clearly audible overtone. An example of a solid
attacks can be served by pronouncing interjections indicating annoyance,
dissatisfaction, indignation: “Oh, what a shame!” During a solid attack,
causes excessive tension on the vocal cords.
During a soft attack, the moment of closure of the ligaments and the beginning of exhalation coincide, and
Immediately after contact, the ligaments begin to vibrate. For example:
“Oh, how nice it is here!” A soft attack is considered the most common and
a physiologically based way of activating the vocal
ligaments, as it has a positive effect on the sound quality of the voice.
During an inhalation attack, the exhaled air begins to pass through
blow through the glottis until the vocal cords close, and you can hear
the sound of air friction against the edges of the cords, and only then the vocal cords close -
and begin to vibrate. An example of an aspirate attack is pro-
pronunciation of Ukrainian and English or German h in combination with after-
blowing vowel, for example in the word Ganna (Ukrainian pronunciation) or in
the German word haben.
In infants, a cry expressing dissatisfaction is accompanied by a firm voice.
attack, and babbling, expressing satisfaction and calmness, occurs
dit during soft attack
The human vocal apparatus consists of the respiratory organs, the larynx with vocal cords and air resonator cavities (nasal, oral, nasopharynx and pharynx). The resonator sizes are larger for low voices than for high voices.
The larynx is formed by three unpaired cartilages: cricoid, thyroid (Adam's apple) and epiglottis - and three paired ones: arytenoid, Santorini and Wriesberg. The main cartilage is the cricoid. At the back of it, two arytenoid cartilages of a triangular shape are located symmetrically on the right and left sides, movably articulated with its posterior part. When the muscles contracting, pulling back the outer ends of the arytenoid cartilages, and the intercartilaginous muscles relax, the arytenoid cartilages rotate around their axis and the glottis opens wide, necessary for inhalation. With the contraction of the muscles located between the arytenoid cartilages and the tension of the vocal cords, the glottis takes the form of two tightly stretched parallel muscle ridges, which occurs when protecting the respiratory tract from foreign bodies. In humans, the true vocal cords are located in the sagittal direction from the internal angle of the junction of the plates of the thyroid cartilage to the vocal processes of the arytenoid cartilages. The true vocal cords include the internal thyroarytenoid muscles.
Lengthening of the ligaments occurs when the muscles located in front between the thyroid and cricoid cartilages contract. In this case, the thyroid cartilage, rotating on the joints located in the posterior part of the cricoid cartilage, tilts forward; its upper part, to which the ligaments are attached, extends from the posterior wall of the cricoid and arytenoid cartilages, which is accompanied by an increase in the length of the ligaments. There is a certain relationship between the degree of tension of the vocal cords and the pressure of air coming from the lungs. The more the ligaments close, the more pressure the air leaving the lungs puts on them. Consequently, the main role in regulating the voice belongs to the degree of tension of the muscles of the vocal cords and the sufficient amount of air pressure under them created by the respiratory system. As a rule, the ability to speak is preceded by a deep breath.
Innervation of the larynx. In an adult, the mucous membrane of the larynx contains numerous receptors located where the mucous membrane directly covers the cartilage. There are three reflexogenic zones: 1) around the entrance to the larynx, on the posterior surface of the epiglottis and along the edges of the aryepiglottic folds. 2) on the anterior surface of the arytenoid cartilages and in the space between their vocal processes, 3) on the inner surface of the cricoid cartilage, in a strip 0.5 cm wide under the vocal cords. The first and second receptor zones are diverse. In an adult, they touch only at the apices of the arytenoid cartilages. Surface receptors of both zones are located in the path of inhaled air and perceive tactile, temperature, chemical and pain stimuli. They are involved in the reflex regulation of breathing, voice formation and in the protective reflex of closing the glottis. Deeply located receptors of both zones are located in the perichondrium, in the places of muscle attachment, in the pointed parts of the vocal processes. They become irritated during voice production, signaling changes in the position of the cartilages and contractions of the muscles of the vocal apparatus. Uniform receptors of the third zone are located in the path of exhaled air and are irritated by fluctuations in air pressure during exhalation.
Since muscle spindles are not found in the muscles of the human larynx, unlike other skeletal muscles, the function of proprioceptors is performed by deep receptors of the first and second zones.
Most of the afferent fibers of the larynx pass as part of the superior laryngeal nerve, and a smaller part - as part of the inferior laryngeal nerve, which is a continuation of the laryngeal recurrent nerve. Efferent fibers to the cricothyroid muscle pass in the external branch of the superior laryngeal nerve, and to the remaining muscles of the larynx - in the recurrent nerve.
Theory of voice formation. To form a voice and produce speech sounds, air pressure under the vocal cords is required, which is created by the expiratory muscles. However, speech sounds are not caused by passive vibrations of the vocal cords by a current of air from the lungs, vibrating their edges, but by active contraction of the muscles of the vocal cords. From the medulla oblongata to the internal thyroarytenoid muscles of the true vocal cords, efferent impulses arrive via the recurrent nerves with a frequency of 500 per 1 s (for the middle voice). Due to the transmission of impulses at different frequencies in individual groups of fibers of the recurrent nerve, the number of efferent impulses can double, up to 1000 per 1 s. Since in the human vocal cords all the muscle fibers are woven, like the teeth of a comb, into the elastic tissue that covers each vocal cord from the inside, a volley of impulses from the recurrent nerve is very accurately reproduced on the free edge of the ligament. Each muscle fiber contracts with extreme speed. The duration of the muscle potential is 0.8 ms. The latency period of the vocal cord muscles is much shorter than that of other muscles. These muscles are distinguished by exceptional fatigue, resistance to oxygen starvation, which indicates the very high efficiency of the biochemical processes occurring in them, and extreme sensitivity to the action of hormones.
The muscle contractions of the vocal cords are approximately 10 times the maximum air capacity beneath them. The pressure under the vocal cords is mainly regulated by the contraction of bronchial smooth muscle. When you inhale, it relaxes somewhat, and when you exhale, the inspiratory striated muscles relax, and the smooth muscles of the bronchi contract. The frequency of the fundamental tone of the voice is equal to the frequency of efferent impulses entering the muscles of the vocal cords, which depends on the emotional state. The higher the voice, the less chronaxy the recurrent nerve and vocal cord muscles are.
During the production of speech sounds (phonation), all the muscle fibers of the vocal cords simultaneously contract in a rhythm exactly equal to the frequency of the voice. Vibration of the vocal cords is the result of rapid rhythmic contractions of the muscle fibers of the vocal cords caused by volleys of efferent impulses from the recurrent nerve. In the absence of air flow from the lungs, the muscle fibers of the vocal cords contract, but there is no sound. Therefore, to produce speech sounds, contraction of the muscles of the vocal cords and the flow of air through the glottis are necessary.
The vocal cords subtly respond to the amount of air pressure beneath them. The strength and tension of the internal muscles of the larynx are very diverse and change not only with the strengthening and raising of the voice, but also with its different timbres, even when pronouncing each vowel. The range of the voice can vary within about two octaves (an octave is a frequency interval corresponding to a 2-fold increase in the frequency of sound vibrations). The following voice registers are distinguished: bass - 80-341 vibrations per 1 s, tenor - 128-518, alto - 170-683, soprano - 246-1024.
The vocal register depends on the frequency of contractions of the muscle fibers of the vocal cords, therefore, on the frequency of the efferent impulses of the recurrent nerve. But the length of the vocal cords also matters. In men, due to the large size of the larynx and vocal cords, the voice is lower than in children and women, by approximately an octave. Bass vocal cords are 2.5 times thicker than sopranos. The pitch of the voice depends on the frequency of vibration of the vocal cords: the more often they vibrate, the higher the voice.
During puberty, the size of the larynx increases significantly in male adolescents. The resulting lengthening of the vocal cords leads to a lowering of the voice register.
The pitch of the sound produced by the larynx does not depend on the amount of air pressure under the vocal cords and does not change when it increases or decreases. The air pressure beneath them affects only the intensity of the sound formed in the larynx (the strength of the voice), which is small at low pressure and increases parabolically with a linear increase in pressure. Sound intensity is measured by power in watts or microwatts per square meter (W/m2, μW/m2). The voice power during a normal conversation is approximately 10 microwatts. The weakest speech sounds have a power of 0.01 microwatts. The sound pressure level for an average spoken voice is 70 dB (decibel).
The strength of the voice depends on the amplitude of vibration of the vocal cords, therefore, on the pressure under the cords. The more pressure, the stronger. Voice timbre is characterized by the presence of certain partial tones, or overtones, in the sound. There are more than 20 overtones in the human voice, of which the first 5-6 are the loudest with a number of vibrations of 256-1024 per 1 s. The timbre of the voice depends on the shape of the resonator cavities.
Resonator cavities have a huge influence on the act of speech. since the pronunciation of vowels and consonants does not depend on the larynx, which determines only the pitch of the sound, but on the shape of the oral cavity and pharynx and the relative position of the organs located in them. The shape and volume of the oral cavity and pharynx vary widely due to the exceptional mobility of the tongue, movements of the soft palate and lower jaw, contractions of the pharyngeal constrictors and movements of the epiglottis. The walls of these cavities are soft, so forced vibrations are excited in them by sounds of different frequencies and in a fairly wide range. In addition, the oral cavity is a resonator with a large opening into the external space and therefore emits sound, or is a sound antenna.
The cavity of the nasopharynx, lying to the side of the main air flow, can be a sound filter, absorbing certain tones and not letting them out. When the soft palate is lifted upward until it touches the back wall of the pharynx, the nose and nasopharynx are completely separated from the oral cavity and are excluded as resonators, while sound waves propagate into space through the open mouth. When all vowels are formed without exception, the resonator cavity is divided into two parts, connected by a narrow gap. As a result, two different resonant frequencies are formed. When pronouncing “u”, “o”, “a”, a narrowing is formed between the root of the tongue and the palatal valve, and when phonating “e” and “i” - between the tongue raised upward and the hard palate. Thus, two resonators are obtained: the rear one - large volume (low tone) and the front one - narrow, small (high tone). Opening the mouth increases the resonator tone and its attenuation. The lips, teeth, hard and soft palate, tongue, epiglottis, pharyngeal walls and false ligaments have a great influence on the sound quality and character of the vowel. When consonants are formed, the sound is caused not only by the vocal cords, but also by the friction of air strings between the teeth (s), between the tongue and the hard palate (g, z, w, h) or between the tongue and the soft palate (d, j), between the lips ( b, p), between the tongue and teeth (d, t), with intermittent movement of the tongue (p), with the sound of the nasal cavity (m, n). When vowels are phonated, overtones are enhanced regardless of the fundamental tone. These increasing overtones are called formants.
Formants are resonant amplifications corresponding to the natural frequency of the vocal tract. The maximum number of them depends on its total length. An adult male may have 7 formants, but 2-3 formants are important for distinguishing speech sounds.
Each of the five main vowels is characterized by formants of different heights. For “y” the number of oscillations in 1 s is 260-315, “o” - 520-615, “a” - 650-775, “e” - 580-650, “i” 2500-2700. In addition to these tones, each vowel has even higher formants - up to 2500-3500. A consonant sound is a modified vowel that appears when there is an obstacle to the sound wave coming from the larynx in the oral and nasal cavities. In this case, parts of the wave collide with each other and noise arises.
Main speech - phoneme. Phonemes do not coincide with sound; they can consist of more than one sound. The set of phonemes in different languages is different. There are 42 phonemes in the Russian language. Phonemes retain unchanged distinctive features - a spectrum of tones of a certain intensity and duration. A phoneme can have several formants, for example “a” contains 2 main formants - 900 and 1500 Hz, “and” - 300 and 3000 Hz. The phonemes of consonants have the highest frequency (“s” - 8000 Hz, “f” - 12,000 Hz). Speech uses sounds from 100 to 12,000 Hz.
The difference between loud speech and whispering depends on the function of the vocal cords. When whispering, the noise of air friction against the blunt edge of the vocal cord occurs as it passes through a moderately narrowed glottis. During loud speech, due to the position of the vocal processes, the sharp edges of the vocal cords are directed towards the air stream. The variety of speech sounds depends on the muscles of the vocal apparatus. It is caused mainly by contraction of the muscles of the lips, tongue, lower jaw, soft palate, pharynx and larynx.
The muscles of the larynx perform three functions: 1) opening the vocal cords during inhalation, 2) closing them while protecting the airways, and 3) voice production.
Consequently, during oral speech, a very complex and subtle coordination of the speech muscles occurs, caused by the cerebral hemispheres and primarily by the speech analyzers located in them, which occurs due to hearing and the influx of afferent kinesthetic impulses from the organs of speech and breathing, which are combined with impulses from all external and internal analyzers. This complex coordination of movements of the muscles of the larynx, vocal cords, soft palate, lips, tongue, lower jaw and respiratory muscles that provide oral speech is called articulation. It is carried out by a complex system of conditioned and unconditioned reflexes of these muscles.
In the process of speech formation, the motor activity of the speech apparatus transforms into aerodynamic phenomena and then into acoustic ones.
Under the control of auditory feedback, kinesthetic feedback is activated continuously when pronouncing words. When a person thinks, but does not utter words (inner speech), kinesthetic impulses arrive in volleys, with unequal intensity and different durations of intervals between them. When solving new and difficult problems in the mind, the strongest kinesthetic impulses enter the nervous system. When listening to speech for the purpose of memorizing, these impulses are also large.
Human hearing is unequally sensitive to sounds of different frequencies. A person not only hears the sounds of speech, but also simultaneously reproduces them with his vocal apparatus in a very reduced form. Therefore, in addition to hearing, proprioceptors of the vocal apparatus are involved in speech perception, especially vibration receptors located in the mucous membrane under the ligaments and in the soft palate. Irritation of vibration receptors increases the tone of the sympathetic nervous system and thereby changes the functions of the respiratory and vocal apparatus.
Most of Husson's opponents conducted experiments on animals (dogs, cats). The difficulty here, however, is that the results of not every experiment can be mechanically transferred to humans, since the human vocal muscle has a number of distinctive properties. Husson refers to these distinctive properties when putting forward his theory. Similar experiments on humans can be carried out only in exceptional cases, during forced surgery on the larynx, and even then with the consent of the patient.
Nevertheless, there is still reason to believe that the regulation of the frequency of vibrations of the vocal cords in humans is a rather complex process, in which, under all conditions, the role of myelastic forces and air pressure can hardly be ignored. Even in the last century, the German physiologist I. Müller was able to show that the pitch of the tone emitted by the isolated human larynx can be varied in fundamentally two ways: by the tension force of the vocal cords at constant air pressure and by the force of subglottic air pressure with constant tension of the ligaments. Why couldn’t these simplest mechanisms be used by nature to regulate the pitch of the fundamental tone of the voice in a living organism? To clarify the question of the role of air pressure, the following experiments were carried out (Medvedev, Morozov, 1966).
While the singer was playing a note, the air pressure in his mouth was artificially changed using a special device. The magnitude of this pressure and the vibration frequency of the vocal cords were recorded on an oscilloscope. As can be seen in the oscillogram, despite the fact that the singer was instructed to keep the pitch of the note unchanged, the fundamental tone of his voice still involuntarily increased or decreased depending on the pressure in the oral cavity (Fig. 17). An artificial increase in pressure in the mouth led to a decrease in the frequency of the fundamental tone until the vibrations of the vocal cords completely stopped, and a decrease in pressure again led to an increase in the fundamental pitch of the voice. At the same time, it was found that the less experienced the singer, the more his fundamental frequency “walks” when the pressure in the oral cavity is artificially changed.
Finally, in another series of experiments the condition of complete naturalness of phonation was not violated at all. The singers were given the task of periodically changing the sweat of a certain height when singing, that is, reducing or increasing the force of subglottic pressure, while trying not to change the pitch of the fundamental tone of the voice at all. The strength of the voice also changed from forte to piano. Both the strength of the voice and the frequency of vibration of the singer's vocal cords were continuously recorded and measured with special devices. The graph (Fig. 18) clearly shows that with a wave-like change in voice strength, and therefore pressure in the lungs, the vibration frequency of the vocal cords also involuntarily changes (albeit within small limits), increasing slightly with increasing voice strength and decreasing with decreasing subglottic pressure.
This fact is well known from everyday experience: in ordinary conversational speech, don’t we raise the main tone of our voice when we want to shout louder and, conversely, don’t we lower the volume when talking quietly? It’s not for nothing that a person who begins to speak loudly is told: “Don’t raise your voice!”
Rice. 18. Changes in the vibration frequency of a person’s vocal cords when the strength of the voice changes. The solid line is the fundamental frequency; intermittent - voice strength In conventional units; arrow - direction of voice amplification and increase in fundamental frequency; horizontally - time from the beginning of phonation (in seconds).
It goes without saying that if the frequency of vibration of a person’s vocal cords were completely independent of pressure (more precisely, on the difference between subglottic and supraglottic pressure), then we would not have detected such changes in the vibrations of the ligaments. However, they are detected, and this can be seen in many other examples.
If a singer is given the task of singing all the notes - from the lowest to the highest - with a voice of equal strength, for example forte, then you can guarantee that not a single singer can withstand the same strength of voice on all notes. He will sing the lowest notes much more quietly than the highest ones (see, for example, Fig. 6). Numerous studies show that the involuntary increase in vocal strength as the pitch rises is a pattern among singers. Thus, in order to sing low sweats, the singer must necessarily reduce the pressure in the lungs. At the same time, increasing subglottic pressure helps the singer reach high notes. True, a singer can, within certain limits, change the strength of his voice without changing its height, but these limits are still limited: within a wide range, the height of the voice depends on strength, just as strength depends on height.
The above experiments and observations, although they are not a direct contradiction to Husson’s main idea about the central neuromotor nature of the vibration of the human vocal cords, still force one to be cautious about his statements about the complete independence of the frequency of oscillation of the vocal cords from the underlying air pressure.
The voice apparatus is a living acoustic device, and, therefore, in addition to physiological laws, it also obeys all the laws of acoustics and mechanics. And turning to musical acoustics, we see that the pitch of musical instruments is regulated by simply tensioning the string or varying the size of the vibrating reeds (Konstantinov, 1939). The pitch of some whistles (f0) is determined by the relationship f0=kvр, where p is the amount of air pressure, k is the proportionality coefficient. There is evidence that the frequency of vibration of the vocal cords of the human larynx (all other things being equal) is also determined by this very ratio (Fant, 1964). Further, we see that the shorter the singer's vocal cords, the higher his voice. In addition, basses have vocal cords two and a half times thicker than sopranos. According to research by L.B. Dmitriev, the size of the resonators for singers with low voices is naturally larger than for singers with high voices (Dmitriev, 1955). Isn't this whole mechanic related to the pitch of the voice? This is certainly true!
The facts say that the acoustic-mechanical laws governing the frequency of vibration of the vocal cords undoubtedly take place in a living organism, and it would hardly be fair to discount them. Even if we are extremely friendly towards Husson and fully recognize the existence of a “third function” of the human vocal cords, there is still no reason to think that this “third function” is the only monopoly regulator of the frequency of vibrations of the cords. The human vocal apparatus is an extremely complex device and, like any complex apparatus, it apparently has not one, but several regulatory mechanisms, to a certain extent independent of each other, controlled by the central nervous system. This ensures amazing accuracy and reliability of the voice apparatus in a wide variety of conditions.
These arguments, however, in no way diminish the role of the central nervous system in regulating the vocal cords. On the contrary: it must be emphasized that the regulation of all myelastic and mechanical properties of the vocal cords (the degree of their tension, closure, density, etc.) and aerodynamic conditions in the larynx (regulation of subglottic pressure, etc.) is entirely carried out by the central nervous system. The nervous system is in charge of all this acoustics and mechanics. The central nervous system is helped in this complex process by numerous sensitive formations (proprioceptors and baroreceptors), sending information to the nerve centers about the degree of contraction of various muscles of the larynx and the entire respiratory tract, as well as about the degree of air pressure in the lungs and trachea. The role of these internal sensitive formations (receptors) in the regulation of vocal function is well identified in the works of Soviet researchers V. N. Chernigovsky (1960), M. S. Gracheva (1963), M. V. Sergievsky (1950), V. I. Medvedev with co-authors (1959), as well as in the experiments of Husson himself.
The research of R. Husson and his colleagues undoubtedly has great progressive significance in the development of the physiology of phonation: they attract the attention of scientists to this important problem, stimulate new searches and already today explain what is difficult to explain from old positions. Undoubtedly, a large scientific debate around a new theory is also useful, since every day it brings us more and more new knowledge. Truth is born in dispute.
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