示振器

Kaleidophon \Ka*lei"do*phon\, Kaleidophone \Ka*lei"do*phone\,
[Gr. ? beautiful + ? appearance, form + ? sound.] (Physics.)
An instrument invented by Professor Wheatstone, consisting of
a reflecting knob at the end of a vibrating rod or thin
plate, for making visible, in the motion of a point of light
reflected from the knob, the paths or curves corresponding
with the musical notes produced by the vibrations.