The Undersea World of Sound

Snorts, clicks,
whistles, groans
- tune in to the long-distance language of the ocean

The vast ocean of the world are dark, deep and mysterious place where eyesight counts for a little as soon as you venture very far beneath the surface.
   For humans, who lived in a world dominated by visual stimuli, to exits in such condition would be impossible. But for whales and dolphin that live in the ocean or in the case of a few species, muddy rivers and estuaries, the darkness is unimportant. what is crucial to them is sound.
   Sound is efficient way to transmit and sense information, especially as it travels five times faster trough water than trough air. if humans shout to someone, it is unlikely that they will be heard a kilometer away. But if a whale 'shouts' in an ocean channel, another whale may hear it tens, if not hundreds of kilometers away.
   Whale and dolphin use sound in two ways : communication and for echolocation. Dolphins, porpoises, and toothed whales communicate through a wide variety of high-frequency sounds - pure ton whistles, pulsed squeals, screams or barks - generally at frequencies of 500Hz to 20Hz (where hertz is a cycle per second and a kilohertz a thousand).
   But as well as using sound to communicate, toothed whales and dolphins also rely on echolocation to learn about their immediate environment, including prey that might be lurking nearby. They produce intense short broad-band pulses of sound in the ultrasonic range. of between 0.25 and 220 kHz. These clicks are brief - typically less than one millisecond long, but they are repeated many times each second.