Page 45 - Damen Shipyards Group

44 SUSTAINABILITY SPECIAL 45

Underwater

sound reduction

“If you cause your ship to stop and place the
head of a long tube in the water and place
the outside extremity to your ear, you will
hear ships at a great distance from you.”

The statement itself does not come as a surprise – the connected
nature of water molecules relative to, say, air molecules, simply put,
ensures sound can travel a lot further underwater. What is perhaps
surprising about this is that, when Leonardo da Vinci said it, it was 1490
and ships did not yet have engines.
Cutting cavitation

Significant shipping “Quite signifi cantly, in fact,” rejoins Edwin. “The biggest part of the
Leaving aside for now complexities relating to different frequencies issue comes from cavitation caused by sub-optimally performing
and hearing ranges and keeping things simple, it’s easy to imagine that Taking a different path propellers. By identifying this and optimising the propeller and other
underwater sound today is both more prevalent and loud. In fact, it’s Many shipyards outsource the profi ling of underwater sound to related parts – nozzles, rudder, even the hull form – we drastically
been estimated that underwater sound has doubled every ten years for classifi cation societies or specialist companies, but Damen has always reduce the level of underwater sound. At the same time, the optimal
the past six decades. chosen not to follow this path. performance of the propeller has a direct and signifi cant impact on
on a reel, all of which are lowered overboard to the seabed, and a reducing fuel consumption and thus, emissions. This brings together
There are numerous factors – military activity, offshore energy “Doing it in-house is cost-effective for our clients. It also gives battery powered date recorder, a laptop and a ship-tracking GPS two benefi ts for ship owners; attention to underwater sound also
exploration and operations and, of course, shipping. Shipping is confi dence to some clients keen to maintain confi dentiality about their system, operated on board a support vessel. generates energy effi ciency.”
the most signifi cant. It’s certainly not the loudest, but it is the most vessels’ performance – for example, navies. Besides, it makes sense
widespread and, as vessels ply their trade across oceans and seas, to measure underwater noise on our own vessels, in the same way Location, location, location Damen’s underwater sound research is developing towards greater
day and night, throughout the seasons, the sounds of shipping are we look at characteristics such as speed or bollard pull, for example. It’s a relatively simple piece of equipment, though it usage is not ecological usage. Damen was recently approached by KNVTS (Royal
unceasing. Adding underwater sound measurement to our scope gives us control without challenges. Dutch Association of Marine Technicians) to give a presentation on a
of a wider part of the shipbuilding process.” “It’s diffi cult to fi nd a suitable place for carrying out the measurements. chosen topic. Having realised the potential of what they could do in
The effects this has on marine life are poorly understood, though it’s Location is key. The sea fl oor must be fi rm. The water must be deep – the fi eld of underwater sound, Damen selected underwater sound as
clear that there are effects. Perhaps the most obvious impact is that Continuing in the loop between 50 and 100 metres. And there must be no background noise.” its subject.
on marine mammals. These creatures have evolved using sound to To these ends, Damen R&D has developed a continual ship design Given that sound travels so much farther in water, this requires a
communicate with each other and to locate their pray. Interruptions in feedback loop based on four stages: predict levels, adjust design remote area. “We approached ecological experts Ecomare – specialised in seals in
sound can literally compromise marine mammals’ survival. accordingly, measure levels, update model. Norwegian good the North Sea to cooperate with us on this. We placed our focus on
Moving down the chain Tjakko Keizer, principal research engineer at Damen, has been working “The Norwegian Fjords are good, as NATO navies have long known. two things – what is the effect of underwater sound, so far as we know,
to marine life and, based on this, what technology have we designed
There are indications that the impact of underwater noise may go further on underwater sound levels on Damen vessels for almost a decade. Though given the right environment, we are able to use the system on to improve the situation inside and outside of our vessels.”
down the food chain too. That, for example, fi sh larvae may be killed “If I look back, it started in 2001 with the Irish research vessel Celtic location. We’ve used it in Indonesia, for example on the PKR (frigates
by the sounds of pile driving as offshore construction takes place, that Explorer. We made a good start; she’s still the benchmark in quiet for the Indonesian Navy) and also in the Black Sea to demonstrate the Regulation ready
certain creatures may suffer not only hearing damage, but also undergo underwater sound today. compliance of the Baía Farta with the contractually agreed underwater Following this, Damen was invited to join a consortium organised by
behavioural changes as a result – even very straightforward changes like sound levels. the International Fund for Animal Welfare (IFAW), Rijkswaterstaat and
loss of sleep. “Then it was a while before we were called upon to design something partners including marine biologists, government bodies and research
with quiet performance in mind. In 2011 we started again with a new “We are planning to use it again soon on the RSV Nuyina, Australia’s institutes as well as industry representatives.
Damen is well positioned to assist with the development of quieter research ship for Belgium. After that it went fast – there was one after Antarctic Supply and Research Vessel that we are currently constructing
ships – it’s something the shipbuilder has been working on for many years another. The latest has been the Baía Farta fi shery research vessel for at Damen Shipyards Galati.” “Participation in the consortium enables us to anticipate changes in
already, as Damen’s Manager R&D valorisation Edwin van Buren explains: Angola. the market. Combined with the experience we already have, we are
“We have been conducting research into the underwater sound profi le The fi ndings of Damen’s work on underwater sound, though not able to respond quickly. The technology is clear, the measurements are
of our ships for many years. To begin with, this had little to with “Then there were the SIGMA vessels (modularly built corvettes and originally aiming specifi cally at improved ecological performance, clear. Our job now is to look at how to combine the two and develop
ecology, but with ensuring the quiet operation of, for example, naval frigates) – this is what we developed the measuring system for initially.” did, however, turn out to improve the sustainability of its vessels’ solutions. The need for this going forwards couldn’t be clearer. Advice
ships and research vessels.” The system he refers to is the patented Damen Underwater Sound performance. for best practice as regards underwater sound is there already, it’s
Measurement System. The system is a mobile, modular one that highly likely such recommendations will pass into regulation. And when
features a hydrophone, tetrahedral cage and long measurement cables they do, we’re ready.”