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In this week’s programme Adam Walton is exploring the diversity of sounds you can hear in the ocean depths.

Beneath our seas there’s a very different soundscape from the one we’re used to on land. We might imagine the underwater world to be a silent one but the oceans are actually surprisingly noisy – from the songs of whales and other sea mammals to the clicking, chattering, ticking and grunting of a whole range of fish and crustaceans.Ìý Then there are the man-made noises from ships’ engines, sonar and industry. And,Ìýif you have the right equipment, you can hear the sounds of the natural movement of the Earth itself.

There’s a whole family of different waves which propagate through the ocean – either on the surface, through the water or along the sea bed.ÌýBroadly they can be divided into two types: gravity waves and elastic waves.Ìý Dr. Dick Hazelwood from the Institute of Acoustics gives us a quick guide to these waves. Adam talks to Cardiff University mathematician Dr. Usama Kadri about the high-speed acoustic gravity waves which are generated by undersea earthquakes and how these waves could be used to give advance warning of a tsunami.

We also hear from Phil Johnston, a marine acoustic specialist. He tells Adam about the technique of passive acoustic monitoring which is used to monitor undersea sounds, particularly those of marine mammals. He also explains how man-made sounds are an increasing problem for species which depend on sound to communicate and navigate underwater.

Finally, Adam speaks to Tim Gordon, a marine biologist from the University of Exeter. He’s also studying in the impacts of man-made sound on our oceans and he tells Adam how his research has taken him all over the world -Ìý from the Arctic to where he’s working right now, the Great Barrier Reef off the coast of Australia.

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