Recommendation ITU-T P.57 specifies the electro-acoustical characteristics of artificial ears to be used for telephonometric measurements. Three devices are specified: a telephone band type for measurements on traditional telephone sets, an insert earphone type and a type faithfully reproducing the characteristics of the human ear.

The latter type (type 3) is specified in four configurations. The requirements of the third one (type 3.3  Pinna simulator) have been slightly modified in this revision of Recommendation ITU‑T P.57 by specifying its construction by a softer elastomer.

Besides this, the description of the applicability of all couplers has been changed, now allowing for an overlap in their usability according to the receiver type under test.