thermophone

American  

[thur-muh-fohn] / ˈθɜr məˌfoʊn /

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.

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Etymology

Origin of thermophone

First recorded in 1875–80; thermo- + -phone