Ask HN: How do radio stations quantify their listenership?

2 points by iamshs ↗ HN
Measuring number of visitors on a website is easy due to visitor pinging the server. Measuring TV viewership is explained here: http://electronics.howstuffworks.com/question433.htm. But how does a radio station track how many users are listening in, or which show is most popular?

2 comments

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But it does not say about radio. The concentration is more on viewership. https://en.wikipedia.org/wiki/Portable_People_Meter

Edit: This is the link inside that article, which leads to http://www.colemaninsights.com/sites/colemaninsights.com/fil...

So I think they select random people to carry their device, which listens to radio stations tuned in by the user. Radio stations are identified by the embedded sub-audible codes. The device then phones home conveying the metadata. Interesting. Thanks.