Sounding out in the deep

Humans make a lot of noise when they are out on the seven seas. An interactive exhibition showed us just how damaging this is to our deep sea friends.

 Illustration by  Zoe Gillet

Illustration by Zoe Gillet

We tend to think the sounds of the ocean are familiar to us. Popular choices for calming soundtracks often include waves crashing against the seashore, seagulls gawking as they patrol the beach and other sounds reminiscent of some tropical paradise. But these sounds are quickly left behind when imagining the mysterious depths of the ocean, where it is generally assumed to be a dark and silent void.

At 100 metres under the sea, beyond the reach of the sun’s rays, visible light fades away to hardly one percent of its surface intensity and vision is quickly ruled an unreliable sense. Although sound is different underwater, the ocean is far from silent. Below the crashing waves on the sea surface, soundwaves become the key to survival.

Cetaceans, more affectionately known as whales, dolphins and porpoises, have well-adapted auditory systems allowing them to take advantage of the unique acoustic properties of their aquatic environment. Acoustic signals allow whales and dolphins to not only communicate with one another, but to navigate the oceans and hunt or forage for food. Even the world’s largest known animals rely almost completely on acoustics to function efficiently. Sound is their sight.

 
  The  frequen sea   exhibition held in Dunedin, NZ used a string model of noise to convey how acoustics from human activity are creating obstacles for cetaceans.   ©  Katharina Marino (used with permission)

The frequensea exhibition held in Dunedin, NZ used a string model of noise to convey how acoustics from human activity are creating obstacles for cetaceans. © Katharina Marino (used with permission)

 

As a species that is so heavily dependent on visual cues, it is difficult to imagine living day-to-day life with only clues from acoustic signals. Instead of asking visitors to close their eyes and accomplish a task, the frequensea exhibition was designed to visibly translate the experience of seeing by hearing to visitors. The exhibition, created as part of a master’s thesis for University of Otago’s Centre for Science Communication, took place over 10 days between September and October 2017. The project’s aim was to engage the community in Dunedin, New Zealand with the problematic effects of marine noise pollution by creating an art installation that required the participation of the public.

Hosted in an underground basement, visitors were given the illusion of submerging themselves underwater as they walked from the street down steps into the exhibition space. Visitors were greeted by a soundtrack of southern right whale calls, which are then rudely interrupted by underwater recordings of seismic blasts, sonar signals and cargo vessels, as well as a slew of other human activities that are contributing to the commotion we’re making in our oceans.

The higher density of molecules in water allows sound to travel significantly further and about five times faster than it does through air (to account for this, a land mammal would need five times the space between each ear just to appropriately pick up one complete soundwave — even a fennec fox would need adapters to properly pick up that kind of signal). Sound energy is created by pressure fluctuations or mechanical vibrations propagating through the water. The resulting soundwaves are influenced by, and will change in frequency and velocity depending on, the properties of the water they travel through.

 
  Cetaceans, such as whales and dolphins, use acoustic signals underwater as a form of communication and sight.   Christopher Michel/Flickr  (CC BY 2.0)

Cetaceans, such as whales and dolphins, use acoustic signals underwater as a form of communication and sight. Christopher Michel/Flickr (CC BY 2.0)

 

As whales approach the surface their acoustic signals travel faster in the warmer waters, but once they dive below 2000 metres, pressure becomes the dictating factor. In between these temperature and pressure zones, sounds hit the Sound Fixing and Ranging (SOFAR) channel, a sweet spot for acoustic propagation where sound may travel thousands of kilometres. Unlike humans that use air channelled through the outer ear, many cetaceans hear sounds through a thin, fatty section of the lower jaw known as the pan bone. Each of these factors affect the way our marine neighbours experience and process underwater acoustics.

Although we might not all be as talented as our good friend Dory who has so eloquently demonstrated her fluency in whale, we do know that cetaceans use a variety of combinations of frequencies, duration and tones for their acoustic signals. Baleen whales, such as the southern right whale or famous singing humpback whale, generally use low-frequency sounds that can propagate long distances — in some cases, across entire ocean basins. Toothed whales and dolphins use high-frequency sounds to create clicks for communication and echolocation.

In the undisturbed ocean, there are still plenty of sounds creating their own underwater symphony. High-frequency sounds above the 200 Hz mark are created by wind, waves and precipitation on the sea surface. Below 20 Hz, earthquakes and tectonic activity rumble along accounting for the majority of low-frequency sounds. Pre-industrialisation, there was an open 'frequency sound window' in the band between 20 Hz and 200 Hz. It is here that cetaceans and other marine life evolved to emit and pick up acoustic signals.

However, improved technology has allowed human activities to move further away from the coastlines into the open ocean — and our increased physical presence also increases our acoustic imprint. Increased anthropogenic sound has caused ambient noise in the ocean to rise by 10 to 100 fold. As we search for oil using seismic surveying, transport goods on commercial ships, implement harbour construction, patrol our country’s aquatic boundaries with sonar and travel the world on giant cruise liners, we interrupt the ambient sound of the world’s oceans with more and more noise. 

 
  Participants chose from five coloured strings in the exhibition that represent different human activities that produce a lot of noise in the ocean.   ©   Urban Dream Brokerage  (used with permission)

Participants chose from five coloured strings in the exhibition that represent different human activities that produce a lot of noise in the ocean. © Urban Dream Brokerage (used with permission)

 

Nested within an open layout, the centre of the exhibition represented the world’s oceans with a string model of noise. Two sets of columns running through the centre of the space were outfitted with hooks and theatre lights. As visitors entered, they were invited to take a coloured elastic string and attach it to a hook under its corresponding light. They then stretched it across to another column. Each of the five colours of string represented one human activity that is a significant contributor to marine noise pollution (commercial shipping, military sonar, harbour construction, cruise ships or seismic surveying).

The more visitors there were, the more strings were contributed to the model and the more web-like the space became. All of this made it more challenging for subsequent visitors to move through, representing the same issues cetaceans are having to overcome as they are forced to change and adapt their lives with the increase of anthropogenic activities.

From inside the string model of noise, visitors were accompanied by photo and video projections of southern right whales, which framed the model on opposing walls. Courtesy of National Geographic photographer Brian Skerry and Dunedin-based filmmaker Bill Morris, the images gave visitors a peek at the lives of these giants of the deep, further providing visitors with the illusion of being submerged underwater as they navigated through the ‘noise’.

 
  The full extent to which cetaceans will be able to adapt to rising marine noise pollution is still unclear.   Amaury Laporte/Flickr  (CC BY-NC 2.0)

The full extent to which cetaceans will be able to adapt to rising marine noise pollution is still unclear. Amaury Laporte/Flickr (CC BY-NC 2.0)

 

Imagine you are at a party where the music is turned up, everyone is shouting and you’re trying to hold a conversation. With every volume notch the stereo goes up, the more you raise your voice to be heard — or you may just give up trying to talk altogether. Now imagine never being able to escape the sound even if you leave the room, the house or even the neighbourhood. It is easy to assume that you would have elevated levels of stress and irritation. Each of these reactions are similar to those marine biologists have observed in whales and dolphins in areas where the waters have been invaded by anthropogenic noises.

The rise of marine noise pollution hinders the ability of cetaceans to efficiently perform basic functions without having to adapt and change. Whether temporary or permanent, these changes may interrupt individuals, groups or even an entire species’ behaviour. The full extent to which cetaceans are able to adapt to the increased sound is unknown. But we do know that we are essentially blinding them with all the racket our industrial activities are causing.

Once visitors made it through the string model of noise, they reached several other information exhibits that demonstrated the overall presence of human activity on both a global and local scale. Graphic visualisations provided visitors insight on the number of ships traveling in and out of Dunedin’s Otago Harbour, as well as average gross tonnage and associated decibel levels created by these vessels. Data requested from Port Otago indicates that a total of 366 ships were in the harbour from the months of January through September 2017. The average decibel associated with the average sized ship was 121 dB. Although sound is different underwater, humans exposed to sounds at 120 dB are likely to suffer immediate hearing damage.

 
  The increase in industrialised human activity on the water, including movement of container ships, has led to underwater noise pollution.   Skitterphoto, Pexels  (CC0)

The increase in industrialised human activity on the water, including movement of container ships, has led to underwater noise pollution. Skitterphoto, Pexels (CC0)

 

Information panels were paired with a map showing the number of reported cetacean sightings in and around the harbour. Visitors were also able to listen to the individual sound clips that played throughout the exhibition soundtrack on an interactive iPad. Each of the 19 sound clips were visually represented with soundwave icons to show the differences in frequency between sounds such as southern right whale calls and sonar signals. The last component was a visualisation, Ship Map, developed by Kiln, which depicted every merchant vessel in the oceans over the course of 2012. Visitors could see the shipping routes, type of cargo carried and several other factors for any individual day of the year. Each of these was meant to build upon their experience in the string model of noise.

The visual and participatory nature of the exhibition provided visitors a tangible experience encouraging a better understanding of the issue of marine noise pollution. Visitor reactions to the frequensea exhibition highlighted the overall lack of awareness of the issue. Because the effects of sound are not easily captured in a photograph or a video clip that can go viral on social media, the issue is generally unknown to the public. Human activity in the oceans is sure to keep rising as technology and demands for goods continue to grow. It may be unrealistic to assume that we can eliminate all noise, but the solution is significantly easier than that of trash pollution, which still requires a significant amount of clean up (even if we could eliminate all littering today). We can turn down the volume.

The exhibition had a clear message for visitors: the key to protecting the health and wellbeing of whales and dolphins is creating policies that will regulate anthropogenic activities in the ocean. Some of these include open ocean speed limits, protected marine environments and improved understanding of cetacean use of acoustics.As soon as the noise is turned down or turned off, there is no outstanding physical clean up for humans to take care of. The residual effects of changed behavioural patterns and high stress levels will simply take time to rehabilitate. And for any of this to be made possible, the first step is for the public to hear just how much noise we make.

Edited by John Back