Acoustic head simulator. This device is a type of head and torso simulator (HATS). It is used to simulate the shape and acoustical properties of the human head, including the external ears (pinnas). It is equipped with ear simulators representing the ear canals, with microphones at the positions corresponding to the eardrums. The sound levels produced at the eardrum microphones are equivalent to the sound levels produced at the eardrums of a normal human adult listening to the same sound source. Photographed at the National Physical Laboratory in Teddington, UK.