The bodies of 40 pilot whales were found on India's Andaman coast in October, prompting an investigation into a military sonar system described as "the loudest sound in the sea."
Scientists suspect the culprit in the mysterious deaths, first reported in late October, is a low-frequency active sonar used to locate submarines and loud enough to kill whales and dolphins.
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Whales and dolphins are highly sensitive to sonar, on which they depend to navigate and hunt. The sonar used by the Indian military was loud enough to kill them at 240 decibels, writes the Hindustan Times.
New research about the effects of loud noises on the nervous systems of whales and dolphins had fanned controversy over the use of powerful sonar systems by militaries around the world in recent years.
Off-shore sonar from Scottish wind farms has been linked to an increased number of whale beachings, writes the Telegraph.
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The Natural Resources Defense Committee states that the effects of loud sonar on cetaceans, such as whales and dolphins, can include bleeding around the brain and bubbles in the organs — essentially a case of the "bends," the deadly condition most often linked to human scuba divers.
It's also suspected that the sonar makes it harder for the animals to find food and interact with each other, and can increase their stress levels to a dangerous degree — an effect similar to constant blasting of music at dangerous volumes for people.
Recent studies indicate that sonar does enhance stress levels in pilot whales, which are endangered.