An acoustic device consisting of a rigid cavity with one or more small openings. When exposed to sound or vibration, a Helmholtz resonator responds most strongly near a characteristic resonance frequency governed by the dimensions of its cavity and openings. A common example is a bottle or jug that produces sound near its resonance frequency when air is blown over the neck's opening. The Helmholtz resonator is named after the physicist and physiologist Hermann von Helmholtz, who constructed spherical glass resonators with small openings at opposite ends to analyze the frequency content of sounds, including musical tones.