In making objective electro-acoustic measurements on telephones, the human mouth and ear are replaced by a sound for driving the handset microphone and by an acoustic coupler for terminating the receiver. The sound source is referred to as an artificial mouth and consists of a moving coil loudspeaker housed in a small enclosure with supplementary acoustic circuit elements leading to a single sound port. The acoustic coupler is referred to as an artificial ear and consists of a microphone in a terminating air volume, often with supplementary acoustic circuit elements. The artificial mouth, together with a source of electrical energy, is often referred to as an artificial voice; however, this term should properly be reserved for those cases in which the resulting acoustic output is a speech-like signal.