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. [1913 Webster]