Following years of planning and testing, Nielsen is launching a digital tracking service for streaming audio called Nielsen Digital Audio Ratings. According to the release, the service will “measure over-the-air radio listening, across mobile apps and Web players, regardless of ad model and device.” The new service, part of Nielsen’s larger Total Audience initiative, will track data from 2,500 digital AM/FM and e-radio stations across 48 markets. A service to track data for on-demand audio services and podcasts is in development. “Nielsen Digital Audio Ratings allows broadcasters, advertisers and marketers to better understand the dynamics of a station’s over-the-air and online audiences,” said Brad Kelly, managing director for Nielsen Audio.