Vocal Resonance and Puff Oscillations
Jack C. Cotton · The Journal of the Acoustical Society of America · 1937
Experiments indicate that chest or tracheal resonance has little effect on sounds emitted from the mouth. Sound transmitted through the chest wall during phonation has an intensity level 30 decibels or more below the oral sound. Artificial alterations of the oral cavity volume prove that any vowel may be produced without loss of vowel character while the oral cavity dimensions are those characteristic of the vowel (i) as in “machine.” “Nasal resonance” can occur only when the mouth and nose are coupled together (lowered velum). Louder phonation is possible with the velum raised. Sound passing through the velum is attenuated from 20 to 30 decibels. Accessory nasal sinus resonance can affect only nasal sounds, and these negligibly. The glottal puff is an efficient complex sound generator. The abruptness of this puff determines the brilliance or “resonance” of the sound. A sudden puff from any source causes a 2800∼ oscillation of the air. This “atmospheric natural frequency” is responsible for brilliance in good voices. It is the limit approached by a resonator's natural frequency as the orifice is progressively enlarged. It is a function of the effective inertia and elasticity of the air in the region of the puff.