Abstract: A method of operating a first user terminal of a first user, comprising: running a first communication client application on the first user terminal so as to enable the first user terminal to participate in a group communication session over a network with respective communication clients running on other user terminals; receiving, by the first user terminal, a plurality of audio data streams, each carrying audio data generated at a respective one of the other user terminals; the first communication client associating each of the received audio data streams with a respective user of one said other user terminals; the first communication client outputting the received audio data streams through one or more audio output devices associated with the first user terminal; and independently controlling, within an audible range, an output volume level of at least a selected one of the received audio data streams output through the one or more audio output devices.