Abstract: An audio beacon system, apparatus and method for collecting information on a panelist's exposure to media. An audio beacon is configured as on-device encoding technology that is operative in a processing device (e.g., cell phone, PDA, PC) to enable the device to encode an environmental sound and transmit it for a predetermined period of time. The acoustically transmitted data is received and processed by a portable audience measurement device, such as Arbitron's Personal People Meter™ (“PPM”), or other specially equipped portable device to enable audience measurement systems to achieve higher levels of detail on panel member activity and greater association of measurement devices to their respective users.