What is "phoneidoscope"

Phoneidoscope \Pho*nei"do*scope\, n. [Phono- + Gr. e'i^dos form + -scope.] (Physics) An instrument for studying the motions of sounding bodies by optical means. It consists of a tube across the end of which is stretched a film of soap solution thin enough to give colored bands, the form and position of which are affected by sonorous vibrations.

n. An instrument for studying the motions of sounding bodies by optical means. It consists of a tube across whose end is stretched a film of soap solution thin enough to give coloured bands, whose form and position are affected by sonorous vibrations.