ClipArt ETC
"Hemholtz constructed a series of resonators, each one of which responds powerfully to a single tone of certain pitch or wavelength. they are metallic vessels, nearly spherical, having an opening, as at A, for the admission of the sound waves." -Avery 1895

Hemholtz Resonator

"Hemholtz constructed a series of resonators, each one of which responds powerfully to a single tone…