Why are some sounds more frightening than others? Are there evolutionary origins behind the things we find scary? And is there anything more blood-curdling than a full throated scream? Becky Ripley and Emily Knight tune in to the sounds that send the shivers down our spines, via a frightened Marmot in the Rocky Mountains of Colorado, and a brand new kind of musical instrument known as the 'apprehension engine'. Beware listeners, you may be in for a fright.... Featuring professor Daniel Blumstein, Chair of the Department of Ecology at UCLA, and film score composer Mark Korven. Produced and presented by Emily Knight and Becky Ripley.