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Shhh, you’re hurting my head

By David, 6 February 2015 News

A whale surfacing to breathe.

A humpback whale’s skull amplifies low frequency sound, helping it to hear noises in the ocean.
Credit: ©istock.com/miblue5

Written by Beth Askham

Researchers have found that whales hear low frequency sounds by amplifying them in their skull bones. Ocean sounds made by humans may be messing with their heads.

Up until now, it’s been a mystery how baleen whales hear sound. Using the skull of a fin whale that had washed up on the beach, researchers have found the answer.

They used a CT scanner to first see inside the skull and then modelled what happens when sound interacts with the whale’s head. They found that the whole skull vibrated, exciting the bony ear complexes that are the whales’ mechanism of hearing. The skull bones amplify and direct noise straight into the whale’s ears.

Baleen whales use baleen plates to filter the ocean water for food. They include humpback whales, blue whales, fin whales and right whales.

The noises they make are very low-frequency moans, grunts, thumps and knocks and some higher frequency noises including whistles and chirps. The low-frequency noises may be a way to communicate with other whales at great distances.

The sounds they make overlap in frequency with the sounds humans make underwater including commercial shipping, military exercises and energy exploration. If these sounds are being amplified to the whale by their skulls, we could be making a whole lot of confusing and disrupting noises in the oceans.

As most baleen whales are endangered this information will perhaps help us regulate and control the amount of noise we make so we don’t disrupt their lives.

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2 comments

  1. So cool!!! What happens with a underwater volcano?

      Reply
    1. Hi Tomas,
      Some underwater volcanoes can be ridiculously loud. The Krakatoa eruption in 1883 was so loud it was heard in Perth, over 3000 kilometres away. The shockwave from the explosion travelled around the world several times, and could still be detected days after the explosion.

      Other eruptions are quite quiet. there are plenty of cool videos on youtube of quiet volcanoes in Hawaii, for example.

      I found a web page with some underwater recordings of interesting sounds, including volcanic tremors and whale song.:

      http://oceanexplorer.noaa.gov/explorations/sound01/background/seasounds/seasounds.html

      Hope this helps!

        Reply

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