This is the second of a two part description of the mechanism of voice production. The first section described sound production by the larynx; this section describes how that sound is modified by the vocal tract to produce speech.

The sound produced by the vocal folds consists of a series of harmonics, shown in a schematic to the left. The lowest harmonic, which is usually the strongest, is called the fundamental frequency. For men the fundamental frequency is about 100 Hz; it is slightly higher in women and children. As the graph shows, the intensity in each harmonic decreases with increasing frequency.

The length of the vocal tract, from vocal folds to lips, is about 17 cm in adults. The shape of the vocal tract will change as we move our tongue, jaw, palate, and lips. Depending on the position of these structures and the overall shape of the vocal tract, certain sound frequencies will be amplified by the tract and others will be dampened. Those frequencies that are amplified are called the formants.

The overall effect of the vocal folds and the vocal tract is shown to the left. The harmonics are modified in amplitude by the transfer function of the vocal tract.
Examples of position of the oral cavity for certain vowels, and the formants produced by that position are shown below. Note that subtle changes in tongue position can produce a significant change in the formant, and therefore a totally different vowel sound.

The process of modifying the shape of the vocal tract to produce different sounds is called articulation.

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Mechanism of Voice Production: Articulation

EXCELLENCE. INTEGRITY. SERVICE. TEAMWORK.
The academic advantage for patient-centered quality health care.