thermophone

[thur-muh-fohn]
noun
  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.

Origin of thermophone

First recorded in 1875–80; thermo- + -phone
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018