Ad agencies and their clients in the USA have welcomed the launch of a ratings measuring system for online radio listening.

Arbitron and comScore Media Metrix have launched a joint venture - with first estimates due next week - which allows media planners and buyers to use the same metrics for online as for traditional radio.

Already signed up are AOL Radio Network, Yahoo's LAUNCHcast and Microsoft's Radio and

Chris Korol, Microsoft product manager, says the two companies are well respected by agencies and advertisers and provide the credibility needed for online radio measurement.

Says Bill Rose, vp of Arbitron New Ventures: "We are combining Arbitron's expertise in radio ratings with comScore's online measurement capabilities to provide the numbers that agencies need to evaluate online radio in the same terms as traditional broadcast media."

Data sourced from (UK); additional content by WARC staff