Fish & Water - Sounds Wild
Undersea Noise

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Undersea noise

The ocean can be a noisy place. The feeding calls of humpback whales resonate in the waters off Point Adolphus in Southeast Alaska...but it isn't long before a tour boat adds engine noise to the undersea soundscape.

The ocean could be noisy even before motor boats arrived on the scene. Near the Marjerie glacier in Glacier Bay, waterfalls, creeks and melting ice create a background of white noise. In Johns Hopkins Inlet, the restless motion of icebergs adds sound, as does a distant calving off the face of the glacier.

Chris Gabriele, a biologist in Glacier Bay National Park, is studying and documenting undersea sounds. She's particularly interested in learning how marine mammals, especially humpback whales, might be affected by the sounds made by ships and boats. Whales experience the world mostly by the way it sounds, rather than by how it looks, since underwater visibility is so limited in plankton-rich Alaska waters.

Whales may move away from preferred feeding areas when disturbed by vessel sounds. Vessel noise can also interfere with whale communication, increase the chance of collision between vessels and whales, or cause short-term hearing loss. Researchers need to learn how much noise is too much, what role the frequency of the sound plays and what effects vessel type, speed, and proximity might have.

While larger vessels like cruise ships are loud at greater distances than smaller vessels, smaller boats can produce equivalent underwater noise levels at close range. But while a skiff with a 100-plus horsepower engine can potentially be as loud as a cruise ship, the volume peaks at different frequencies. Large, low RPM vessels tend to generate and radiate more noise at lower frequencies while noise from small, high RPM craft typically peaks at higher frequencies. It's not known exactly what frequencies baleen whales hear best at, but it is believed they may be more sensitive to lower frequencies, so large vessel may affect their underwater ambient noise habitat from a greater distance.