reVoice

Riva Capellari

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Located in Brookside in the heart of Kansas City


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Amazing Voice

Amazing Voice….
The absolute wonders of the human voice never cease to amaze me, despite the fact I have been singing and teaching voice for more than 30 years. Mechanical complexities can create some of the most simple, but beautiful music.
In this issue we begin to study the mechanics of sound production starting with the three components of an instrument, including the voice: an actuator (air), an oscillator (vocal folds), and resonators (throat and mouth cavities).

Sound is motion. It moves in the form of “the propagation of sound waves radiating from a vibrating body through an elastic medium,” (like air) (Sataloff). Your voice in the air is similar to waves on the surface of water.
Sound also requires energy to set it into motion. In singing, this energy is provided by air pressure from the lungs, the power source for these sound waves. The vocal folds be-come oscillators, creating periodic variations in air pressure that move through the vocal tract as sound waves, releasing into the atmosphere. Self-sustaining oscillation relies on myoelastic-aerodynamic action. Myo refers to muscle; aerodynamic to the airflow which provides the vital steady source of energy for successful sustained vibration.
Can you recall being pushed on a swing as a child? Once the pushing ceased, you had to pump your legs or the swing would slow to a stop from lack of a driving energy source.
Phonation – singing or speaking, begins when the lower edge of the vocal folds are pushed opened from below by air pressure being re-leased from the lungs. (Phonation occurs on exhalation). As the air moves upward through the glottis (the opening between the folds), it separates the top edge of the folds. Simul-taneously, the lower section starts to close. This undulating motion is called the mucosal wave. The tissue that makes up the vocal fold cover (see May issue!) is loosely attached so it moves easily, making it possible for the wave to occur. Vocal fold closure is driven by the tissues’ natural recoil to return the folds to their original shape. Closure is also assisted by the Bernoulli effect (Daniel Bernoulli); the discovery that if a volume of moving air is to remain constant, it needs to move faster through a more constricted space, decreasing the pressure.
Think traffic jam – when three lanes of traffic are forced into one, drivers should actually accelerate, not slow down, through the free lane, speeding up to prevent a back-up of cars. In other words, reducing the pressure. In phonation, as the airflow moves through the narrow glottis, it speeds up, causing negative pressure in its wake. This negative pressure results in a “sucking” action, bring-ing the folds together. The opening and closing actions of the vocal folds work with the muscosal wave to set up the self-sustain- ing oscillation that creates the sounds waves we hear as music.
The onset (the vocal initiation of sound) is important because it influences the type of phonation that follows. The hard or glottal onset results from a tightly squeezed adduc-tion, requiring an increase in air pressure that bursts open the folds with a grunt-like sound. This type of onset usually segues into pressed phonation. The opposite is the soft or aspira-ted onset in which the airflow begins before closure, leading to a breathy tone. The most efficient and optimal onset is a perfect union between the tension and timing of the closure and the air flow.
The laryngeal muscles contribute to four phonatory actions: adduction, abduction, stretching and shortening of the vocal folds. Both the lateral cricoidarytenoids (LCA) and interarytenoids (IA) are adductors, closing the anterior and posterior sections of the vocal folds respectively by rotating and sliding the arytenoids together. The posterior cricoid-arytenoids (PCA) contract in the opposite direction from the LCA and IA to open the folds. (Again, see last issue’s images for the location of these muscles).
The paired cricoidthyroid (CT) muscle elon-gates the vocal folds by pulling the thryroid and cricoid cartilages together anteriorly. These longer, thinner vocal folds produce higher pitches. The thyroidarytenoid (TA) muscle (remember, this is the muscle in the vocal fold) is the primary muscle for pro-ducing low frequencies. Its contraction brings the arytenoids forward, shortening the folds.
So—–the vocal folds elongate for higher pitches and shorten for lower ones. This is not the full story however, as changing length alone is insufficient to raise pitch. For ex-ample, the longest strings in a piano make the lowest sounds (they are also the thickest). The stretched folds are thinner and more rigid, counterbalancing the lowering effect of their length (remember that the folds elongate for higher pitches). Sound con-fusing? Because less of the tissue is vibrating over the length, depth and width of the folds at these higher frequencies, (at times, just a very small edge of the tissue is vibrating), the vocal folds, for mechanical purposes, become short and thin (similar to piano strings that sound out the highest pitches). The only way to obtain this short and thin configuration of the folds is through elongation.
In addition to these conditions, increased subglottal pressure is necessary to start and keep the folds vibrating at these higher fre-quencies. For the lower, slower frequencies, the folds are shortened, but they are also thick and loose, and vibrate throughout the length, depth, and width of the tissue.
How do the vocal folds know what pitches to produce? Involvement by both the nervous system and the laryngeal musculature is re-quired to link what we hear to what we sing. Various receptors of the nervous system acti-vate our auditory system and trigger mechani-cal actions of the larynx to respond to the auditory message. These actions include changes in air pressure, vocal fold stretching, and joint movement.
Vocal intensity, or what we think of as loudness, is influenced by actions above, within and below the larynx. Loudness is a subjective, non-measurable term, whereas intensity is the “measure of power per unit of an area” (Titze). Below the larynx, the in-crease in air pressure vibrates the vocal folds over a greater range of motion (amplitude), resulting in quicker, crisper closures. Within the larynx, the contraction of the TA muscle, through shortening, makes available a wider surface (mass) of the vocal folds for vibration. Both increased amplitude and greater mass contribute to increased intensity. In other words, variations in air pressure and vocal fold adjustments are necessary to monitor intensity and to establish and maintain correct pitch.
An important caveat here is that increased air pressure can raise pitch by elongating and tensing the folds. This can be prevented by the contraction of the TA muscle playing a kind of tug-of-war with the CT muscle to keep the length and tension of the folds in check, allowing increased air pressure to increase volume, without raising the pitch. This deli-cate balance between the air pressure and the adjustment of the folds at this venture is one of the essential skills singers must master. And finally, above the larynx, the vocal tract acts as an amplification system, enhancing the sound before it is released for all to hear. We will investigate this phenomenon of resonance more deeply in upcoming issues
I hope this relatively simplistic explanation (believe it or not!) of a complicated mechani-cal function furthers your understanding of how to begin to make beautiful music!
Sing for Your Summer!!!
Treat yourself this summer! A new beginning voice class starts Tuesday, June 19th from 7-8 p.m. See www.revoice.biz for details. On Saturday, June 30th I am offering another introductory voice class through Commun-iversity. Enrollment is limited! Call 816- 235-1407 to register today!
Principles of Voice Production. Titze, Ingo. Prentice Hall.1994 Your Voice: An Inside View. McCoy, Scott, DMA. Inside View Press. 2004. Vocal Health and Pedagogy. Sataloff, Robert, M.D., D.M.A. Singular Publishing. 1998.

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