Systems, methods and devices for gathering data concerning media usage by predetermined audience members. An audience measurement code in acoustic energy produced by a media receiver is detected by a portable media monitor. The monitor also detects a location code produced in a vicinity of the media...http://www.google.fr/patents/US7471987?utm_source=gb-gplus-shareBrevet US7471987 - Determining location of an audience member having a portable media monitor
Determining location of an audience member having a portable media monitor
