> I've heard a few stories about this device.
>
> I'm curious as to how it technically works. The marketing type material
> refers to an "embedded audio signal" that the device picks up. Is this
> done with a Mic or something?
>
> Can anybody point me to some info on exactly how it works?
>
> I'm just curious, it sounds like a pretty cool system.
>
> Thanks, TTYL

>From my understanding, they add an inaudible "watermark" to the signal.
The watermark uniquely identifies the program stream (whether it be radio,
Internet, or whatever). Stations have an encoder on each stream. People
carry a pager sized box that does have a microphone and listens for the
encoded signal. That is logged along with the date and time. At night, I
believe, the user puts the unit in a charging station which phones home
and dumps its data. Arbitron gathers the data and generates reports. I saw
an article where listenership was shown on a minute by minute basis and
correlated with what the station was playing. You could see people tune
out when a particular song was played. For more info, see
http://72.52.213.140/article/76760 .

This "watermarking" is really pretty amazing. It is also being done in the
audio and video of digital cinema so pirated movies can be tracked.

Harold


-- 
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist