TSL (Time Spent Listening)

Audience indicator for radio. Average of the time spent by the listener, listening to a show, station, or the radio, over a time slot or over the entire day. It is expressed in minutes. Listening time per individual is also occasionally used for television (however, the preferred term is Viewing Time per Viewer. Time Spent Listening differs from Listening Time per Listener (LTL) in that those who never listen are not counted.