How does Voice Production work? – A scientific viewpoint
Have you ever wondered how sound production in the human voice actually works? In this blog I will give you a short scientific outline of the physiology of vocal fold vibration and sound production.
You don’t necessarily need to understand the physiology to sing, but it won’t hurt to have some basic understanding of your voice. It might help you to become a better singer, by becoming a smarter singer.
Sound is produced when aerodynamic forces cause vocal folds to vibrate rapidly. There are sequences of vibratory cycles with different speeds. The speed will determine the pitch.
Slower cycles per second, produce lower pitches, faster cycles per second produce higher pitches. For example: 110 Hz = mens voices/lower pitches, 180-220 Hz = female voices/medium pitch, 300 Hz = children’s voices/higher pitch.
In order to understand vocal fold vibration we need to look at the myoelastic-aerodynamic theory along with the Bernoulli principle.
First the vocal folds are drawn towards each other (adducted) by muscles of the larynx (Lateral Cricothyroid, Interarytenoids and Thyroarytenoids).
These muscles initiate vocal fold vibration but do not contract to continue the vibration.
Once the pressure below the vocal folds reaches a threshold, the vocal folds move away from each other and are blown apart in a bottom-to top movement (see below for a visual representation).
They continue moving until the elastic force from the tissue is greater than the pressure from the air moving between them.
When the maximum is reached, the vocal folds start moving towards each other again.
As the air rushes through the very narrow opening between the vocal folds, it must accelerate to get through. This high speed air creates a suction effect and brings the vocal folds together. This is the Bernoulli Effect.
1. Air moves upward towards the vocal folds in “closed” position
2. & 3. Air pressure opens the bottom of vibrating layers of the vocal folds
4. & 5. Air pressure continues to move upward, now towards the top of the vocal folds, and opens the top
6. – 10. The low pressure created behind the fast-moving air produces a Bernoulli effect which causes a suction effect. The bottom closes, followed by the top
10. Closure of the vocal folds cuts off the air column and releases the air
This is one cycle of vocal fold vibration. The higher the pitch, the more cycles per second will occur. For example, an A4 has 440 cycles per second = 440 Hz.
The Bernoulli Effect
The Bernoulli Effect can easily be demonstrated by taking two sheets of paper, holding them together and blowing across the margin of the papers. The papers are sucked towards each other because the pressure between the sheets is lower than the surrounding pressure, which causes the sheets to come together. Below you will find a picture demonstrating the process of Voice.
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