This Recommendation specifies the artificial ears for telephonometric use. Three types are recommended, covering the different transducers, types, sizes and technologies. The methods of use of the artificial ears are outside the scope of this Recommendation; however, some general rules are provided about the application force and the positioning of transducers.
ITU-T P.57-2011 Referenced Document
ITU-T P.380-2003 Electro-acoustic measurements on headsets Study Group 12
ITU-T P.79-2007 Calculation of loudness ratings for telephone sets (Study Group 12)