Undiscovered depths - A look at the sonics of the sea

"...marine species sense sound in different ways; in many cases, they literally hear sound in their bones"

- Sonic Sea, Ocean Noise Report

Some say that we know more about space than we do about the deep ocean, with figures from the National Ocean Service reporting that ninety five percent has never been seen by human eyes. Considering that our home, the 'pale blue dot' planet earth is seventy percent ocean, that's a vast amount of mystery.

Though, it could be said that the most mesmerising thing about what lies beneath the surface is not about what we haven't seen, but instead what we haven't heard. Let's submerge our imaginations below the surface to discover a universe of subsonic communication, but also to explore how our own man-made sounds may well be severely distressing life and upsetting the balance of the oceans.

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Sound travels much quicker in the ocean, transmitting almost five times faster than it does through air. While the top few metres below sea level are illuminated by the sun, light rapidly diminishes as you drop into the further tens, hundreds and thousands of metres eventually leading to a vast, dark abyss. It is true that many animals who live in the sea have multiple heightened senses, but fish and even more so sea mammals largely rely on extraordinary, complex sonic communications and hearing abilities.

Echolocation Echolocation is a technique that sea mammals use to discover their surroundings, including food that may be close. It is the process of the making sounds and clicks that reflect off objects, causing the echo to bounce back to the animal so that they can sense something is there. The longer the echo takes to return to the animal, the further away the object is. If hunting, the mammal speeds up the sounds and clicks get faster and faster until they sound like a buzz, known as the 'click train'. Even more amazingly, the echoes that return differ depending on the size, shape, direction and make up of the object, allowing the animal to work out all of this information. ​

The Weddell Seal Weddell seals, who populate the Antarctic produce some of most supernatural, and in our eyes incredible sounds of any animal. They spend most of their time beneath the Antarctic ice to avoid predators such as orcas, and dive down to 2,000 metres for up to 45 minutes. We know that they can make 49 different types of sounds (by far the most of any seal, as far as is known). According to the Ocean Conservation Network, their 'signals are complex in frequency, amplitude, and time domain. Not enough is known about these animals to understand what accounts for the complexity.' It really is the case that more we find out about the ocean, the more we realise we don't know... listen to their sounds below:

The most well known and widely seen as the most beautiful form of communication in the sea is a sound that is so powerful, it can travel as far as hundreds of miles. It can be so complex that it changes tone and volume over it's 'song', which can last for as long as 30 minutes, and modifies throughout the lifetime of the animal... this, is the humpback song.

The Humpback Song

"[Humpback whale song is] probably the most complex in the animal kingdom" - Philip Clapham, marine biologist​

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A haunting, beautiful sound that almost doesn't feel as though it comes from planet earth, the male humpback whale song wasn't recorded until the 1950s and wasn't heard by biologists until the 1960s. The first whale communications we heard were picked up by a hydrophone (underwater microphone) which at the time was mostly used by the Navy to detect oncoming enemy submarines. Naval engineers were aware of the sounds for a little while, but a certain story goes that navy engineer and whale lover, Frank Watlington, one of the first to record the sounds in 1964 was convinced that it was the sound of a whale. He invited his friend, Katy Payne, an acoustic biologist aboard his ship to listen and study, where she had this to say: "..tears flowed from our cheeks. We were just completely transfixed and amazed because the sounds are so beautiful, so powerful — so variable. They were, as we learned later, the sounds of just one animal. Just one animal." - Katy Payne, NPR interview​​

The hydrophone The hydrophone has since become our single means of delving into sonic sea life. It works by detecting pressure changes in the water (which are an effect of sound waves) and converting these sound waves to electrical voltage. These signals are then recorded and amplified, allowing us to uncover sounds of the sea. Some sounds have to be sped up to increase pitch, for example the deeper ends of the blue whale call as they are subsonic, meaning that their frequencies are below those that humans have the capacity to hear. Early humpback whale recording in 1964, off the coast of Bermuda:

Other whale vocalisation We now also have a degree of knowledge about the vocalisations of the blue whale, fin whale, sei whale, grey whale, right whale, the orca, and just as of very recently the minke whale, who until recently was known as 'the silent whale'. Apart from one subspecies of blue whale, a group who reside in the Indian ocean off the coast of Sri Lanka that been recorded producing multi-pitch songs of around two minutes, the humpback remains the only whale known to have such a complex song. We've put together the sounds of these whales, using recordings by Ocean Network Canada (have a look at their brilliant work here: http://www.oceannetworks.ca/). Watch below:

Sonic Sea - The Ocean Noise Report

"We humans place great importance on our ability to hear clearly… yet we are showing far less concern for the amount of noise we are generating beneath the waves, causing stress and damage in a world that is enveloped in sound ,in a way we can barely imagine”- Sonic Sea, Ocean Noise Report

Adding to the web of ocean sonics, there have always been a number of other natural sounds at sea... waves, strong winds, ice forming and splitting as well as iceberg acoustics. But over the past 100 or so years, things have changed. Since the industrialisation of the ocean, humans have transport themselves and mass amounts of cargo via huge ships, tested explosives for war, used seismic blasts to detect oil and gas under the ocean floor bed and installed oil drilling rigs. As we learnt with the discovery of the humpback song, navy ships use sonars to detect oncoming enemy vessels, but these sonars can be deafeningly loud.

​​(Picture: Sonic Sea) Sonic Sea, a film about oceanic noise pollution, published an Ocean Noise report last year highlighting these impacts which found that overall, these elements drown out sea animals communication and other natural sounds. Furthermore though, they can seriously physically injure them sea life and as a result of stress and confusion, cause displacement. Particular research of these effects on whales specifically, links high intensity naval sonars and blasts of oil exploration to mass stranding events and dangerous diving behaviours, that cause the equivalent damage of severe decompression sickness and brain bleeds in humans.

(Picture: Sonic Sea: sonicsea.org)

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"They are calling still, some effectively yelling to be heard above the din. As we are creating the ever increasing noise, it is up to us to hear them, and to turn down the noise in the ocean." The report does stress that 'in many cases, relatively simple solutions exist to mitigate these problems; what is needed is the political will.' and offers a list of recommendations to controlling the problems, and you can read the full report here: http://sonicsea.org/sites/default/files/IFAW_OceanNoiseReport_WEB_spreads.pdf Watch the trailer for the film:

Find out more on the issue: National Geographic: http://news.nationalgeographic.com/2017/06/seismic-survey-air-gun-oil-gas-exploration-zooplankton-spd/ BBC: Costing the Earth, Sounds of the Seas: http://www.bbc.co.uk/programmes/b068w44v So, a beautiful, fascinating and largely undiscovered world that all too familiarly is at risk from human behaviour. Let's keep a close eye on research developments and keep informed on both the brilliant explorations, but also how we can stop our noisy impact on the ocean.

Finally, to finish on a lighter note...