Sound Systems Of The Sea

The underwater world can be a dark and murky place, so many creatures rely on sound to survive. But some species are adapting their acoustic calling cards in exciting new ways.

- Michelle Meyer

In oceans around the world, marine animals are making quite a noise. It’s long been known that cetaceans such as whales and dolphins use sound to locate food, to navigate and to communicate, but new research is revealing fascinating other uses for this underwater orchestra – from evading predators to ‘whispering’ to their young.

The science of locating objects by sound is known as echolocation (or biosonar). Many species, including toothed whales and dolphins, bats, swiftlets, oilbirds and shrews, use the behaviour to ‘picture’ their environment via sound. Echolocating animals emit calls, locating and identifying objects through the returning echoes. It’s a highly specialised system that can be used for navigation, foraging and hunting.

Whales and dolphins echolocate by throwing out beams of high-frequency clicks in the direction they are facing, much like sonar on a submarine. (Frequency relates to how high or low a sound is. For example, the beat of a bass drum and a rumble of thunder are low-frequency sounds; a piercing whistle and a child’s squeal are high-frequency sounds.)

These clicks are created by passing air through the skull, specifically through the bony nares (nostrils) and across the phonic lips (structures that project into the nasal passage). When air passes through the phonic lips, the surrounding tissue vibrates, producing the sound (see box on p71).