Nielsen Audio (formerly Arbitron) is a consumer research company in the United States that collects listener data on radio broadcasting audiences.

It was founded as the American Research Bureau by Jim Seiler in 1949 and became national by merging with Los Angeles-based Coffin, Cooper, and Clay in the early 1950s.

As a condition of the deal to allow a monopoly, Nielsen must license its ratings data and technology to a third party for eight years.

[citation needed] Responding to requests from its customers—radio broadcasters, ad agencies and advertisers—that expressed their interest in the collection of more accurate ratings data, Arbitron introduced the Portable People Meter (PPM) service in 2007.

[9] The PPM is a wearable portable device, much like a pager or mobile phone, that electronically gathers subaudible codes that identify the source of a broadcast, such as a radio station.

As of December 2009, the PPM was measured in 33 media markets, including Houston, Philadelphia, Pittsburgh, New York City, Atlanta, Detroit, Long Island, Middlesex-Somerset-Union, Chicago, Los Angeles, Riverside-San Bernardino, San Francisco, Jacksonville, Baltimore, and San Jose.