Abstract: An apparatus for transmitting audio tokens includes an acoustic transmitter to generate a range of audio frequencies including an infrasonic range, a sonic range, and an ultrasonic range. An audio token generator assembles the audio tokens, which include a timestamp and an identifier, and modulates the audio token in to the range of audio frequencies. A synchronizer determines the timestamp relative to an input audio stream and a mixer mixes the audio stream and the audio token for presentation by the acoustic transmitter. An apparatus for receiving the audio tokens includes an acoustic receiver to receive the range of audio frequencies. An audio token extractor extracts the audio token including the timestamp and the identifier from the range of audio frequencies. An interpreter determines user information responsive to at least one of the timestamp and the identifier and a user interface element present the user information to a user.