The human oral cavity functions as an adjustable Helmholtz resonator

Evidence

Everyone has adjustable Helmholtz resonators with them at all times. The oral cavity is always available. Shape your mouth for the letter o as in “go,” close off the air passage at the back of the tongue, and flick an index finger against a cheek. A low-frequency, short-lived Helmholtz resonance tone is produced. The resonance frequency can be controlled with the diameter of the opening of the lips, and with the volume of the oral cavity. A tone for a closed cavity can be heard if the lips are closed entirely. Notice the difference in pitch if the mouth cavity is formed, lips are sealed, and the passage to the nasal cavity is open versus closed. — Eric J. Heller, Why You Hear What You Hear- An…, 1211

Categorization

• SEED: The mouth-as-resonator experiment is a concrete demonstration angle for explaining Helmholtz resonance to a general audience.