One of the parts of a TRANSDUCER involved in the conversion of mechanical energy to electrical energy, or vice versa.

The diaphragm is the membrane whose physical motion corresponds to the acoustical vibration being received or emitted; for instance, the part of a MICROPHONE on which the pressure of the SOUND WAVE acts, or the part of a LOUDSPEAKER activated by electrical energy to produce an acoustic vibration. Diaphragms serve a similar purpose in air horns, car horns and the like. See LOUDSPEAKER for diagram.