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Meaning of thermophone

ther•mo•phone

Pronunciation: (thûr'mu-fōn"), [key]
— n.
  1. an electroacoustic transducer that forms sound waves by the expansion and contraction of the air adjacent to a conductor that varies in temperature according to the magnitude of the current passing through it; formerly used to calibrate microphones.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.