Helmholtz resonators amplify tones by exposing the eardrum to internal cavity pressure

Evidence

The principle is not near-field capture (NFC), since the source may not be close by, nor is the source made louder, except inside the resonator. The idea is to set up a Helmholtz resonance in the usual way and then listen to what is happening on the inside of the resonator. The sound is much louder there, but we normally cannot hear it. However, if a small nipple protrudes out the back of the resonator, tightly sealed in the ear canal, the nipple and short air cavity leading to the tympanum become part of the inside cavity. The tympanum is subjected to the full SPL inside the resonator, greatly enhancing any partial present at the resonator’s frequency. This is why Helmholtz resonators work so well, a fact seemingly almost forgotten since Koenig’s day. — Eric J. Heller, Why You Hear What You Hear- An…, 2059

Categorization

• DEFINE: Explains the actual mechanism by which Helmholtz resonators enhance sound pressure at the eardrum.