Resonating device

A resonating device is a structure used by an animal that improves the quality of its vocalizations through amplifying the sound produced via acoustic resonance. The benefit of such an adaptation is that the call's volume increases while lessening the necessary energy expenditure otherwise required to make such a sound. The resulting sound may also radiate more efficiently throughout the environment.

The resonator may take the form of a hollow (a resonant space), a chamber (referred to as a resonating chamber), or an otherwise air-filled cavity (such as an air sac) which may be part of, or adjacent to, the animal's sound-producing organ, or it may be a structure entirely outside of the animal's body (part of the environment). Such structures use a similar principle to wind instruments, in that both utilize a resonator to amplify the soundwave that will ultimately be uttered.

Such structures are widespread throughout the animal kingdom, as sound production is important in the social lives of various animals. Arthropods developed their resonating devices from various parts of their anatomy; bony fish often utilize their swim bladders as a resonating chamber; various tetrapods developed resonating devices in parts of their respiratory tract, and evidence suggests that dinosaurs possessed them as well. Vocalizations produced through zoological resonating devices act as mating calls, territorial calls, and other communication calls.