Noise Pollution is a Big Threat to Blue Whales — Here’s How Scientists Are Listening In
A deep dive into the hydrophone arrays and specific equipment used by scientists at Project Blue Whale at the University of Iceland.
Edited by EE Staff
Cool Stuff
Jan 19, 2026
Growing up to 30 m long and 180 tons, the blue whale is the largest animal in the world. In addition to its impressive size, its calls can be heard thousands of kilometers away and far below the ocean’s surface. But there’s a growing threat to their communication: noise pollution.
These highly intelligent — and endangered — animals have a similar communication frequency range as a variety of man-made sounds, such as ship engines, low-frequency active sonar, seismic air gun array explorations, other oil exploration activities, and more. With growing evidence that noise interference can disturb vital life functions of these whales — feeding, breeding, navigation, and communication — and with underwater noise pollution on the rise, it’s imperative that researchers gain a better understanding of how, why, and where blue whales communicate, as well as the level and effect of noise disturbance on their lives.
Project Blue Whale
The Húsavík Research Center at the University of Iceland is a leading authority in the study of marine mammals. The center is led by Dr Marianne Helene Rasmussen, who is the driving force behind Project Blue Whale, a research project dedicated to gaining knowledge about blue whales in the Northeast Atlantic Ocean to better understand the impact of increasing ship noise on their habitat.
The project aimed to better understand the blue whale’s communication patterns. This required the localization of individual blue whales and the recording of what sounds they were making at what times. Scientists wanted to answer key questions such as whether it was always the same animal calling, what the difference is between animals, and whether they are able to change the frequency of their calls to account for background noise (something other species of whales are able to do).
The project also aimed to find out if and how underwater ship noises affect these communications, which involved projecting noises at certain frequencies to mask the sounds created by blue whales and investigate their responses.
Hydrophones in Marine Research
Dr. Rasmussen came to the project with broad experience in marine research using hydrophone arrays to record beam patterns and sound levels. In an earlier project in Northern Norway, her team recorded the sounds made by sperm whales using Type 8101 hydrophones from Brüel & Kjær. The project had been a great success, so it was a natural decision to use the same equipment again for Project Blue Whale.
The Brüel & Kjær NOTAR recorder allows underwater sound recording for hours at a time — even without the need of a laptop. NOTAR is a small and rugged solid-state recorder that has no shock-sensitive moving parts (unlike tape recorders or PC hard drives) which means it can be used in locations where no PC-based recorder can operate. Hydrophone Type 8106 has a built-in preamplifier which gives a signal suitable for transmission over long cables. It is usable down to 1000 m ocean depth.
Recording the Whales
To record the whales, a digital recorder was custom made at Aarhus University and specially configured to be able to capture sound on one channel and to give an accurate GPS signal reading on the other for precise localization data.
To get accurate recordings, the team also needed calm seas and no wind; otherwise, the subsequent waves and ‘cable strumming’ noise from the hydrophone cables would cause additional noise interference that would render the results useless.
The frequencies of interest were as low as 10 – 20 Hz. In order to achieve any bearing (directivity), the distance between the hydrophones had to be far enough apart to secure a certain minimum angle. The team utilized four boats and four hydrophones in a large hydrophone array; the distance between the hydrophones was either 1 km or 500 m and they were at a depth of 30 m.
Once a whale was sighted, all that was needed was for the boats to stay in place and record the whale sounds and locations for approximately one hour at a time.
Analyzing the Whale Recordings
Aside from a few days of bad weather and some minor technical glitches, everything went as planned and the team managed to gather over 100 whale calls, along with a wealth of good positional data. The recordings were then analyzed onshore.
Of course, the study didn’t end there. The second part — examining how ship noises mask and affect the whales’ communication — is an ongoing project. Nevertheless, the data so far has already revealed some interesting results about the nature of these fascinating sea mammals, how they communicate, what frequencies they use, why, and when.
These findings are, in turn, giving rise to a host of new questions, such as whether or not blue whales can change frequencies when calling, if there is any interspecies communication, and if this methodology can be used to study other types of whales.Never one to sit still, Dr Rasmussen is already planning to apply for financial backing for a range of other projects to look more closely into these and other areas. For a project like this to have gone so smoothly so far, with so many extraneous variables to manage and overcome, is a huge achievement.Project Blue Whale has not only helped to form a far deeper understanding of blue whales — Dr. Rasmussen and her team also hope that their results will be a catalyst for a new dialogue with authorities about shipping lane regulations and other safeguards to the whales’ natural habitat.
And if all this leads to more and better ways of protecting this enormous, endangered, and enigmatic sea creature, then this is the best possible result.
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