\Pho*nau"to*graph\, n. [Phono- + Gr. ? self +
-graph.] (Physics)
An instrument by means of which a sound can be made to
produce a visible trace or record of itself. It consists
essentially of a resonant vessel, usually of paraboloidal
form, closed at one end by a flexible membrane. A stylus
attached to some point of the membrane records the movements
of the latter, as it vibrates, upon a moving cylinder or
plate.