Microphone

Mi″cro‐phone (mī″krō̍‐fōn), n. [Micro- + Gr. φωνή sound, voice: cf. F. microphone.] (Physics) An instrument for intensifying and making audible very feeble sounds. It produces its effects by the changes of intensity in an electric current, occasioned by the variations in the contact resistance of conducting bodies, especially of imperfect conductors, under the action of acoustic vibrations.