How the PPM works

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By The Associated Press

The radio industry is overhauling the way it counts listeners, moving away from a pencil-and-paper diary method in use since the 1960s in favor of a pager-like device called a Portable People Meter.

A group of people are selected to carry around the device, which detects signals embedded in radio broadcasts. The idea is to measure what broadcasts people actually hear, not what they remember hearing.

The new ratings system was developed by Arbitron Inc., the same company that does the diary-based ratings. It's already in use in Houston and Philadelphia, and New York, Los Angeles and Chicago are up next. Arbitron hopes to have the top 10 markets using the system by the end of 2008.

Here's how it works:

Radio stations get a piece of hardware from Arbitron that embeds audio codes in the broadcast identifying the station. The codes can't be heard by humans, but can be picked up by the Portable People Meter.

Listeners who agree to participate are paid a fee, and wear the device from the moment they get up in the morning to when they go to bed at night. A motion detector in the unit can tell whether the device is being worn. If it isn't, its data will be discarded.

At night, the listener places the device in a dock that both recharges the battery and takes in the data of all the radio broadcasts that were captured that day.

That information is sent to Arbitron electronically, which then compiles the data from the various users in the city and crunches the information into ratings for each station.

While Arbitron has had some difficulty meeting the target sample sizes in Houston and Philadelphia, radio executives generally feel that change to electronic measurement is long overdue, and that it represents a major improvement over the diary method.

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