A method for calibrating a hands-free system is provided. The hands-free system comprising a hands-free unit and a mobile phone, the method comprising the following steps of setting up a connection between the hands-free system and a distant terminal via a mobile telephony network of the mobile phone, transmitting a predetermined test signal from one of the hands-free system and the distant terminal to the other of the hands-free system and the distant terminal, the predetermined test signal being provided in both the hands-free system and the distant terminal as reference test signal, comparing the received test signal to the reference test signal stored in the other of the hands-free system and the distant terminal, and determining the calibration parameters of the hands-free system in accordance with the comparison.