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How does changing the shape of the vocal tract create different vowel sounds?

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Uncover the science behind the transformation of sounds into speech — speech Speech is the faculty of producing articulated sounds, which, when blended together, form language.

Vowel sounds are produced by shaping the vocal tract to act as a series of variable resonators. As the vocal cords vibrate, they create a complex sound wave consisting of a fundamental frequency and higher harmonics. This sound is then radiated into the supraglottic vocal tract, which includes the pharynx, oral cavity, and nasal passages.1

By adjusting the position of the tongue, the soft palate, and the pharyngeal musculature, the size and shape of these resonating chambers are altered. This process of shaping the vocal tract determines the modulation of the voice through resonance and damping, which emphasizes specific frequencies known as formants.12

The frequencies of the first three formants are the primary factors that characterize different vowels. Essentially, changing the vocal tract shape changes which harmonics are enhanced or dampened, resulting in the distinct acoustic qualities we perceive as different vowel sounds.21