Abstract: According to the present invention there is provided a method of analysis of the audience for channels selectable by a channel selector device for presentation on a presentation device, the channel selector device providing data indicating which channels are selected and the lengths of time for which selected channels remain selected. The data relating to the lengths of time for which channels remain selected is subject to a capping procedure, whereby the indicated length of time for which a channel remains selected is reduced to a capped maximum permitted length of time if the indicated length of time exceeds the maximum permitted length, to provide capped data.

Abstract: Aspects of the invention relate to an audio matching system for detecting matching of audio signals. In one embodiment, the system comprises a digital signature generation device configured to generate signatures from an audio signal. The device may comprise a signal energy analyser, an event detector, a signature generator, and a transmitter. Embodiments may further include an audio signal comparing device that comprises a receiver, an event locator arranged to use the event data of the received digital signature to locate corresponding portions of another sampled data segment of another audio signal, and an event analyser arranged to analyse the corresponding portions located by the event locator and to determine whether they match the predetermined events of the event data, to thereby determine whether the audio signals match.