A system and method that allows different participants in a conference call to be identified at a receiving terminal includes watermarking speech data when the uplink information from the terminals of the participants is received at the telecommunications network. The speech data is then combined at a conference bridge in the network and is transmitted in the downlink to the receiving terminal. The receiving terminal uses the watermarks to identify from which of the participants the received speech data originated and is operable to reproduce the speech data from the respective participants at different positions in a 2D or 3D space to help the user of the receiver terminal to identify contributions made by the respective participants.