In awe of the ear, Aubrey examines some amazing feats of hearing used by animals to ensure their survival, as well as looking into the latest research on animal eavesdropping.

He does his best to become a barn owl, trying to catch himself a field vole using just his ears, and looks at how birds learn their songs, some starting before their egg has even hatched.

With the help of experts in their field, Aubrey explores the latest research into animal communications networks. Aubrey discovers how members of the same species eavesdrop on each other, as well as eavesdropping on other species around them. At the forefront of our understanding of bioacoustics this research goes way beyond the obvious one-to-one communication and is providing a new window to the natural world.

He also looks at how scientists are able to turn the tables by eavesdropping on the animals and how this is helping in the conservation of many species including bitterns and elephants.

Later in the series, Aubrey goes on an underwater sound safari, discovers sounds human ears are not normally privy to, and samples some of the acoustic hotspots from around the world.