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Launching the hydrophone. Photo: Isak Okkenhaug

Songs from the depths

5 months ago
Written by Ole-Morten Algerøy
Ocean research > Songs from the depths

Songs from the depths

5 months agoOcean research
Written by Ole-Morten Algerøy
Launching the hydrophone. Photo: Isak Okkenhaug

A hydrophone is now installed on board Statsraad Lehmkuhl. A hydrophone is a microphone that works underwater, so that the researchers can listen for songs from the depths.

Under water, there are a lot of different sounds, and sound is transported very well, much better than in the air.

– We can therefore hear sounds from a long distance, says Martin Biuw, who is the group leader for marine mammals at the Institute of Marine Research.

Hydrophones capture all sound underwater, from ship propellers and engine noise to the rumble of earthquakes. But it is first and foremost the sounds whales make Biuw and colleagues are interested in.

The long black rod in the box is the hydrophone. It is fastened to the yellow stabiliser and towed behind the ship.
The long black rod in the box is the hydrophone. It is fastened to the yellow stabiliser and towed behind the ship.

Lots of time under water

The research assistants on board the Statsraad Lehmkuhl have special watch duties, looking for whales. But the whales are only at the surface to breathe occasionally, most of the time they spend down in the depths.

With the hydrophone, the researchers can hear the whales they do not see with the binoculars.

The hydrophone does not just tell if there are whales around the vessel. The different species make different sounds, so the researchers also get to know what kind that swims down there.

Statsraad Lehmkuhl also has an advanced echo sounder on board, which constantly registers how much plankton and other organisms there are below the ship. This helps the researchers understand what is special about the areas where there are a lot of whales.

– Are there high concentrations of plankton? Is there a lot of fish we can catch with the echo sounder? explains Biuw.

Martin Biuw, Norwegian Marine Research Institute Photo: Ole-Morten Algerøy
Martin Biuw, Norwegian Marine Research Institute Photo: Ole-Morten Algerøy

Always on

The hydrophone was delivered when Statsraad Lehmkuhl was docked in Miami. After two days of installation and connection, it was ready for use. Scientists have been waiting to get the hydrophone on board, and it was launched into the sea as soon as the ship was out in open sea on its way to New York.

The plan is to tow the hydrophone behind Statsraad Lehmkuhl the entire voyage around the globe. It is only taken in when the ship sails into the ports.

– Hydrophones are used a lot, but getting data continuously through a circumnavigation is very unique, says Biuw.

Very special

There is one more thing that is special this time. Statsraad Lehmkuhl is a sailing ship. There is no engine thumping and propeller noise interfering.

– It is not common to use a sailing ship to do acoustic investigations like this. The fact that we move so quietly through the sea gives us high quality measurements, says Geir Pedersen, senior researcher at the Institute of Marine Research.

Geir Pedersen, Norwegian Marine Research Institute Photo: Ole-Morten Algerøy
Geir Pedersen, Norwegian Marine Research Institute Photo: Ole-Morten Algerøy

Surprisingly little

Whales are huge animals, but scientists know surprisingly little about them. At least about whales far out to sea.

– Most of the research on whales takes place in coastal areas, says Martin Biuw.

He hopes that One Ocean Expedition can help do something about this. Whales and other marine mammals play a very important role in ecosystems.

– How the life of the largest animals at the top of the food chain is, is a good indicator of the well being of the rest of the ecosystem, says Biuw.

Kjetil Grotle is looking for whales. Photo: Ole-Morten Algerøy
Kjetil Grotle is looking for whales. Photo: Ole-Morten Algerøy

The Gulf Stream

Statsraad Lehmkuhl is sailing across the Gulf Stream on its way up to New York when the hydrophone is finally put to use.

– Where different bodies of water meet, a lot happens. There is a lot of plankton and a lot of fish here, and I hope that means that there are also a lot of whales in these areas, says Biuw.

Hard to handle

The research assistants on board Statsraad Lehmkuhl, Erlend Mundal and Kjetil Grotle, helped install the hydrophone in Miami. Together with boatman Jo Leif Strønen and carpenter Kristian Bülow, they devised a smart installation of the hydrophone on the aft deck.

It is Erlend and Kjetil, and the research assistants who will later take over for them, who are responsible for handling the instrument.

– It is a rather complex system, Kjetil and Erlend explain. We try to document as much as possible of what we have learned, so that we can transfer the knowledge to those who will do this for us.

They completely agree on the gift they hope to get when the ship soon celebrates Christmas in New York.

– Songs from the depths!

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