Phonation

Phonation refers to the production of sound through the vibration of the vocal folds (also known as vocal cords) within the larynx (voice box). It is a crucial component of speech and vocalisation. When the vocal folds vibrate, they create a buzzing or oscillating sound that serves as the foundation for human voice production.

Watch the video below to see how this works.

Here's an overview of the process of phonation^[1]:

1. Respiration

The process begins with respiration, where air is inhaled into the lungs. This is the power source for phonation, providing the airflow needed to set the vocal folds into motion.

2. Phonation Initiation

As air is expelled upwards from the lungs, it passes through the larynx where the vocal folds (vocal cords) are located. The vocal folds are initially in an open position allowing air to flow through. However, during phonation, the vocal folds move towards each other (adduct) and close the pathway. The increased air pressure from the lungs then forces the vocal folds to separate, creating a small opening. This allows a puff of air to pass through. Immediately after, the vocal folds close again.

3. Vibration

The pressure from the airflow builds up beneath the closed vocal folds, causing them to be blown apart.

Once the pressure below the vocal folds drops, the elastic properties of the vocal folds and the action of the laryngeal muscles bring them back together. This cycle repeats at a rapid rate, creating a buzzing sound known as the glottal wave. Each opening and closing cycle represents one vibration or one cycle of sound wave production. The frequency of these cycles determines the pitch of the voice, while the intensity or power of the cycles influences loudness. A faster cycle produces a higher pitch, and a slower cycle produces a lower pitch.

4. Resonance

The sound then travels through the vocal tract (throat, mouth, and nasal cavities), which modifies it, creating the various qualities of the voice. The size and shape of the vocal tract, as well as the position of the articulators (tongue, lips, jaw, and soft palate), determine the resonance characteristics and influence the vocal quality or timbre.

5. Articulation

Finally, the resonated sound is further modified by the movements of the articulators (tongue, lips, jaw, etc.), which form the individual phonemes (distinct units of sound) that make up our spoken language.

Phonation is essential for various forms of communication, including speech, singing, and vocal expression. The manipulation of pitch, loudness, and quality of phonation, in combination with articulatory movements of the vocal tract, allows for the production of a wide range of speech sounds and the conveyance of emotions and intentions through voice.