2. (Physics) An instrument for the mechanical registration
and reproduction of audible sounds, as articulate speech,
etc. It consists of a rotating cylinder or disk covered
with some material easily indented, as tinfoil, wax,
paraffin, etc., above which is a thin plate carrying a
stylus. As the plate vibrates under the influence of a
sound, the stylus makes minute indentations or undulations
in the soft material, and these, when the cylinder or disk
is again turned, set the plate in vibration, and reproduce
the sound.