The revised version of P.581 covers hands-free (including speakerphone, loudspeaking and headset) and handset terminals and include sections for the calibration and use of HATS for handset and headset terminals. This ITU-T Recommendation specifies the use of Head and Torso Simulator (HATS) for speakerphone terminals subjective and objective evaluations (e.g. ITU-T Recommendation P.340). It defines the test arrangements, the mouth calibration, the binaural equalization and loudness summation, as well as the method for headphone calibration to be applied for subjective third-party listening tests as described in ITU-T Recommendation P.832.