So you're an amateur singer, and you're pretty good. Unfortunately the people at the back of the theatre can't hear you hit those exquisite verbrattos. So what can you do? Train your diaphragm! The more air you have at the bottom of your lungs, the more air pressure you have to force those vocal cords open to project your voice to infinity...and beyond. Inspiration occurs when the thoracic cavity expands, and the main muscles involved are the external intercostal muscles and the interchondral portions of the inner and innermost intercostal muscles. But if we recruit the diaphragm, forcing it to contract, the chest cavity will further expand since the abdominal viscera is being compressed by the flattened diaphragm. If you only fill the upper portions of your lungs, then there is less pressure available to rush past the vocal cords through the rima glottis. The result will be a breather and quite voice. However, if the entire chest cavity is filled with air, the higher pressure will allow you to project your voice louder and further! Remember, vocalization all starts with the upward flow of air out of the lungs, so you can't speak when you're breathing in!
2. Pitch and Vocal Quality
Okay hot shot, now the entire audience can hear you. But what about the quality of your voice? Like I said, you're pretty good, but you can be so much better if you trained your intrinsic laryngeal muscles, which as the ones responsible for the vocal cord manipulation to give you that vocal range. There are 5 muscles involved, and their main functions are to abduct, adduct, and tense the vocal cords.
Okay, so first take a deep breath. As you're doing this, the glottis (opening into the larynx) is forced wide open as the posterior cricoarytenoid muscle (PCA) abducts the vocal cords. Now as you begin to hit your first note, you're laryngeal adductor muscles close the glottis by bringing the two vocal folds together. So remember to train your thyroarytenoid (TA), interarytenoid (IA), and later cricoarytenoid (CA) muscles so that the adduction is as efficient as possible! Okay, so the glottis is sealed off, and as you start to expire (releasing the stored air in your lungs) the air pressure beneath the glottis will start to rise. We will call this sub-glottal pressure. Depending on the tension applied to the vocal folds, namely by the actions of the vocals and thyrocricoid muscles, different amounts of sub-glottal pressure will be required to force apart the vocal folds so that the air can escape.
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| a) Movement of the posterior cricoarytenoid muscle; b) Movement of the interarytenoid and lateral cricoarytenoid muscles; c) Movement of the thyroarytenoid muscle (medial portion is the vocalis muscle of the vocal fold) |
The tighter the vocal folds are, the greater the sub-glottal pressure needed cause the vocal folds to vibrate. So a higher pitched voice will be produced since the vibrational oscillations are shorter and faster. If we want to apply some physics terminology, the pitched produced is higher (or of greater frequency) because the oscillating waves on the vocal folds are shorter, and wavelength is inversely proportional to frequency. Likewise, as the vocal folds are relaxed, less sub glottal pressure is required to cause the vocal folds to vbrate. And when they do vibrate, the wavelengths are longer, thus the sound produced is of a lower register.
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| Movement of the cricothyroid muscle on the cricothyroid joint leading to tension of the vocal folds. |
The process in which the vocal fold vibrates as expired air exits through the glottis is explained by the body-cover theory (1). In this theory, the vibrational motion (wavelengths) starts in the sub-glottal portion of the vocal fold. Here the mucosal portion of the vocal fold oscillates over the stiffer ligamentous portions; or more technically stated the superficial lamina propria oscillates upon the vocal ligament composed of the intermediate and deep lamina propria. If you need a refresher on the composition of the vocal ligament click here. This mucosal wave then propagates medially towards the free edge of the vocal fold where it is carried up onto the supra glottal region as the passage of expired air forces the two vocal folds apart. The mucosal wave now moves laterally, away from the glottal opening.
The sound produced by the vibration of the vocal folds resonates through the pharynx (the portion connecting the larynx to the oral/nasal cavities) and out through the mouth. The pharynx itself, as well as the bony sinuses in the skull act as resonating chambers to amplify the sound waves.
3. Pronunciation
Alright, so now you're able to hit those high and low notes with ease. But unfortunately there are lyrics in the song you're going to perform! So how does the bare mechanics of pronunciation work? Well, it all has to do with the shape of your mouth/oral cavity that can be changed through the use of the tongue and lips. If you don't believe me, try speaking while holding your tongues or rolling your lips around your teeth! How difficult was that?
However, this is a very simplified explanation of the pronunciation process. Pronunciation itself involves the complex interplay between the brain and the mechanics of the various muscles involved (besides those mentioned in the mouth and larynx.)
Well, there you have it. You're going to be an astounding vocalist now! So don't be lackadaisical and go get to practicing for your debut! Till next time, cheers!
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References:
1. Simpson C, Rosen C. Operative techniques in laryngology. Berline: Springer;2008.
