Diving Deeper Into the Sound of Blue Whales

Royston, United Kingdom, December 15, 2015 (Newswire.com) - Very little is known about these calls - such as how man-made noises can interfere with them and what the implications really are - so Project Blue Whale was created to dive deeper into these issues. Thanks to the efforts of Dr Marianne Helene Rasmussen and her team, scientists are now beginning to understand more about how, why and when these majestic animals communicate - and what can be done to help them prosper.

Blue whales communicate using the lowest frequency sound recorded among cetaceans with loud, low-pitched moans and whines that can be heard over very large distances. These ‘down-sweep’ calls have frequencies from 107 Hz to 21 Hz (or lower) and show an incredible variety, with eleven different types of sound.

Unfortunately, this is the same frequency range as a wide variety of man-made sounds, such as ship engines, low-frequency active sonar, seismic air gun array explorations and other oil exploration activities, to name but a few. There is growing evidence that noise interference can disturb their vital life functions, such as feeding, breeding, navigation and communication. This is a very serious problem, especially for an endangered species.

Project Blue Whale’s objectives fell into two parts: firstly, the project aimed to gain a better understanding of the communications of blue whales. Dr Rasmussen has broad experience in marine research using hydrophone arrays to record beam patterns and sound levels, as she had been part of a similar project in Andenes in Northern Norway that recorded the sounds made by sperm whales using Type 8101 hydrophones supplied by Brüel & Kjær. The project had been a great success and so it was a natural decision to use the same equipment again for Project Blue Whale.

The blue whales communicate via low frequencies (for a 15 Hz signal, the wavelength is around 100 m) so a special method was also needed to locate exactly where the whales were. This was achieved using four boats positioned in a line, 500 m or 1 km apart, with the hydrophones at a depth of 30 m. Then - once a whale was spotted - the boats just needed to stay in place to record the whale sounds and locations for approximately one hour at a time.

The second part of the project will try to find out if and how underwater ship noises affect these communications.

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