By the back cover page of the book;

Active Listening, Second Edition is a fully updated and revised edition of the popular three-level listening series for adult and young adult learners of North American English.  Each level offers students 16 engaging, task-based units, each built around a topic, function, or grammatical theme.  Grounded in the theory that learners are more successful listeners when they activate their prior knowledge of a topic, the series gives students a frame of reference to make predictions about what they will hear.  Through a careful balance of activities, students learn to listen for main ideas, to listen for details, and to listen and make inferences.