[BC] Arbitron

[Gary Blau]

Jim:

Some basic info from the horse itself:
http://www.arbitron.com/portable_people_meters/home.htm

The encoding is a narrow band psycho acoustically masked data burst 
imbedded into the audio, containing the encoder ID and a time stamp.
The encoder needs some surrounding audio to mask the data, or it won't 
generate anything.  So, if you have dead air, you also have no PPM, and 
thereby no reported listening.

It's also level dependent to some degree, but finding out much detail 
about that is impossible beyond vague generalities.  You probably want 
some AGC in front, especially with a less than balls to the wall pop 
music format.

The 'monitors' we have only give us an idiot light and contact closure 
in the event of a failure.  For that to occur, an entire three minute 
window of zero detected encoding has to pass.  The bursts are normally 
about 5 seconds apart.  If you have only one good 5 second burst in 
three minutes, your monitor tells you you're good:
http://www.w3am.com/PPM.pdf
There is currently no way of telling if you're sending out any of those 
individual bursts, granularity-wise.  You just have to 'assume' that 
everything is fine as long as your idiot light is green.

It's very different than relying on human recall.  There, if someone 
thinks they listened, or wants to admit to listening, you get credit 
even if they really didn't.
With PPM if they aren't exposed to your audio you absolutely won't get 
credit, but if they are and there's some other factor going on we don't 
know all about yet, you may still not get credit.
The upside may be that if they fall asleep in the doc's waiting room the 
soft AC station gets huge numbers.

They're not measuring the same things.

g

Jim Tonne wrote:
> Dana, Blaine and all:
> 
> I am going to reveal a  *gross*  level of ignorance
> on a subject here but please bear with me!
> 
> I have been following the PPM thread for quite a
> while now.
> 
> Just how does this PPM "encoding" work?
> 
> I cannot believe that little "beeps" or something
> that is easily heard would be transmitted.  Surely
> that would drive listeners bonkers.
> 
> I can see perhaps looking at the envelope of the
> audio in the home and comparing it with the
> envelope of the transmitted signal.  Look at a
> transceiver for 30 seconds and compare.
> 
> Perhaps I am not alone in my ignorance of the
> subject . . .
> 
> - JimT