Can sharks hear a hum when something yummy is around?

posted: 04/11/12
More to Explore From HowStuffWorks.c

Sharks have keen hearing, a huge advantage in the ocean since sound travels both farther and faster in water. On top of that, sharks can pick up on very low-pitched noises known as infrasounds. Many oceanic sounds fall into this frequency range — a perfect example is the noise fish make when they're in trouble. Sharks hear this noise and know where they can track down some easy prey.

Scientific studies have proven that when sharks pick up on infrasonic sounds — often their first clue about the location of prey — they usually swim over to the source in a hurry. It works best when the noises come in rapid, irregular bursts, as opposed to continuous or higher-pitched frequencies.

In addition to the sounds of fish swimming around in schools or flailing about after being hooked on a fishing line, other oceanic activities produce low-level frequencies too. Swaying underwater cables and splashing swimmers can make sounds that attract sharks. The more intense the sound, the quicker sharks tend to hit the scene to check it out.

This response to certain frequencies can sometimes lead to a feeding frenzy if too many sharks arrive around the same time. It may also cause problems during certain survival situations. Rescue vehicles like Coast Guard helicopters emit similar low-frequency sound waves, so flying them in after a shipwreck might call unwanted attention to any submerged survivors.

More on
Shark Week