Sonic Kayaks – sound science

11 April 2018

When you swim in the sea and stick your head underwater what do you hear? Waves crashing and rocks clattering? Behind all this, the ocean is as noisy as Manhattan at rush hour and an art-science collaboration in Cornwall, led by FoAM Kernow, has built an instrument to listen in on the cacophony under the surface...

The Sonic Kayak is both a musical and a scientific instrument which allows us to detect submarine sound using underwater microphones, called hydrophones, underneath a kayak. These feed the sound into a simple Raspberry Pi computer, which plays the clicks, squeaks and whirs through speakers above the water. Submerged thermometers also detect changes in water temperature as you paddle along. The temperature data are converted into sound, transforming information into music. The temperature sonification can be heard here: https://youtu.be/-kDDfIeVqcs

As a marine scientist fascinated by the sounds of the sea (and a keen kayaker!) I was eager to get involved. My PhD looked at the noise generated by underwater renewable energy machines, which involved dropping waterproof microphones into the depths of Falmouth Harbour. However it took time for the data to be collected and I had to take the devices back to the lab to hear the recordings. I was drawn to the Sonic Kayak as it allowed me to collect important scientific data whilst enjoying the sounds of the sea in real time.

The Sonic Kayak was built by a diverse team. Invitations were publicised for open hacklab events; programmers developed the code on the Raspberry Pi, researchers helped with honing the data collection and sound artists worked to turn the numbers into music.
Turning data into sound – or sonification – is nothing new. The beep of a heart rate machine is familiar to us all. Sonification allows us to monitor and detect changes without having to constantly look at a screen or dial.

Our oceans are often murky, especially near the coast, and light only penetrates a few metres. With visibility lacking, many marine animals rely on sound to navigate and communicate. Sound travels five times faster underwater than it does in air and can also travel much further. Hearing is therefore a really important sense for marine life but human activity is drowning out natural noise.

Sounds originating from shipping, sonar and construction are now pervasive in our seas. Imagine trying to have a conversation with friends at a loud party. You might be able to communicate with someone sat next to you but not with someone across the room. It’s the same underwater – but worse as sound can travel so much further. Noise pollution in our seas has been shown to reduce the distance at which animals can hear each other [1], cause stress [2, 3] and even lead to temporary or permanent changes to hearing ability [4]. It’s believed that the UK’s largest dolphin stranding, which happened in Falmouth a decade ago, was due to human-generated subsea noise[5].

The beauty of the Sonic Kayak is that, save for the odd splash, it’s a quiet way of collecting data and causes minimal disturbance to animals above and below the surface, especially if you compare it to a motor boat. Being in a kayak means we can easily survey even the shallowest parts of the coastline. Shallow coastal and estuarine areas are of particular importance to society. A lot of fishing takes place here and it’s the busiest area of the sea for recreation too[6]. Additionally, there are lots of variables – the seasons, the weather and input from rivers all impacting coastal waters over a range of time and spatial scales. Traditional monitoring methods, such as satellites[7-9], struggle to capture this variation and surfers have already been considered as a huge potential resource for collecting such variable coastal temperature data[8]. The Sonic Kayaks are equipped with GPS and we are able to use the data collected to map the undersea noise landscape and sea surface temperature at a really fine scale.

We’re increasingly finding that it’s the temperature of this surface water that is important in ocean health, it’s a go-to measure of how climate change is affecting our seas and has also been used in monitoring harmful algal blooms[10].

By listening to the soundscape of our oceans we can also monitor biodiversity. Just as a birdwatcher might listen for bird calls in woodland, we can use the kayak to detect the presence of species it’d be tricky to survey underwater otherwise. A study in France found that areas of the sea where fishing didn’t occur had louder and more diverse sounds than fished areas [11]. The sounds we detect with the Sonic Kayak may be used as a snapshot of ecosystem health.

We’ve shown that it’s possible to modify a kayak and convert it into an important scientific instrument (which is also fun to use!) and we’re now looking at how we can collect even more data, where recreational kayakers can become citizen scientists.

It’s a great experience to enjoy the Cornish coastline whilst listening in on the marine life and it’s been inspiring to work on a citizen science project with collaborators from so many disciplines. We hope it encourages more people to explore the marine habitat and find out about the species that live along our shores and we’d love to hear from you if you’d like to get involved.

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