How Do You Measure "Engagement"?

Researcher and Hear 2.0 blogger Mark Ramsey on The Difference Between “Listening” and “Hearing”:

"...for many listeners radio isn't about high-testing songs and engaging personalities; radio is about comfort. Indeed radio is as much a part of the ambient soundscape as the whistle of the wind, the chirping of the birds, and the songs of the crickets. Something to be heard rather than listened to."