Abstract: Systems and methods are provided for gathering audience measurement data relating to exposure of an audience member to audio data. Audio data is received in a user system and is then encoded with audience measurement data. The encoded audio data is reproduced by the user system, picked up by a monitor and decoded to recover the audience measurement data.

Abstract: The present invention concerns methods and systems for gathering data concerning usage of media data provided from a predetermined receiver to a user. First data concerning usage of the media data is gathered by means of a portable monitor carried on the person of the user. Second data concerning usage of media data by the predetermined receiver is gathered by a monitoring system separate from the portable monitor, the second data corresponding to at least a portion of the first data. Audience measurement data is produced based on the first and second data.