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Discovery of Sound in the Sea
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Echolocation

Marine mammals use sound to obtain information about their surroundings and to find food. They do this by producing sounds or sonar clicks that are reflected back when they strike an object. This is called echolocation. Echolocation is important to marine mammals because it allows them to navigate and feed in the dark at night and in deep or murky water where it is not easy to see. Toothed whales, including beluga whales, sperm whales, dolphins, and porpoises are known to echolocate.

Animation showing a dolphin emitting a signal and the signal bouncing off of some fish and returning to the dolphin

The signals produced by animals during echolocation provide the animal with information about what is in the environment. Toothed whales that use echolocation send high frequency click sounds into the environment. The sounds then bounce off distant objects, and the echoes are received by the animal that produced them. The animal that produced the original echolocation clicks can determine how far away an object is based on the time an echo takes to return. The farther away the object is, the longer it takes for the echo to return.

As an echolocating animal gets closer to its target, the rate at which it produces clicks gets faster and faster. The series of echolocation clicks leading up to a capture attempt of a prey item is called a click train. As the interval between the clicks gets shorter, the click train starts to sound like a buzz.

The returning echoes sound different than the original click produced by the animal. The differences between the sound of the original click and the returning echo provide the echolocating animal with information about the size, shape, orientation, direction, speed, and even composition of the object. Dolphins have an amazing ability to detect a target the size of a golf ball almost a football field away. That distance is much further than a dolphin can possibly see underwater. The beam of the echolocation clicks is also very directional and can be moved with a slight turn of the animal's head.