Media-centric companies are often interested in tracking the number of times that audience members are exposed to media compositions (e.g., television programs, motion pictures, internet videos, radio programs, etc.). To track such exposures, companies often generate audio and/or video signatures (e.g., a representation of some, preferably unique, portion of the media composition or the signal used to transport the media composition) of media compositions that can be used to determine when those media compositions are presented to audience members. The media compositions may be identified by comparing the signatures to a database of reference signatures. Additionally or alternatively, companies transmit identification codes (e.g., watermarks) with media compositions to monitor presentations of those media compositions to audience members by comparing identification codes retrieved from media compositions presented to audience members with reference identification codes stored in a reference database. Like the reference signatures, the reference codes are stored in association with information descriptive of the corresponding media compositions to enable identification of the media compositions.
Audience measurement companies often enlist a plurality of panelists to cooperate in an audience measurement study for a length of time. For example, a panelist may be issued a portable metering device capable of collecting media exposure information indicative of the media to which the panelist is exposed. In such instances, the panelist agrees to carry the portable meter on their person at all times so that the portable meter is exposed to all of the media seen or heard by the panelist.