Fathom, a truly unique sonic event

My home city of Plymouth is in some ways the land that time forgot – it is both beautiful and ugly, rich and very poor, and in the eyes of the shortsighted, too far away from anywhere. But it is the sea that gives the city its identity – it is teasingly glimpsed from hilltops, houses and streets, sometimes offering up breathtaking views of the Eddystone lighthouse, 14 miles out, a massive maritime matchstick that indicates the presence of a deadly sandstone reef, for centuries a lethal threat to all shipping entering the Western reaches of the English Channel.

 

The city rests between two estuaries, the Plym and the Tamar, and despite the fact that the Plym gave up its name to the city, it is the seemingly bottomless Tamar that is the major waterway, dividing Devon from Cornwall and providing a home for the Navy in Devonport, and specifically nuclear submarines which apparently can submerge in the estuary and leave the harbour unseen.  It was a vital link for the once thriving metal and mineral mining industry, and a trade route into north Devon and Cornwall.  Whilst still a busy waterway, it is now a common thread for a wide group of artists of many kinds, and it is art that unexpectedly brought the Tamar and the very forefront of modern audio technology together.

 

John Matthias is Associate Professor in Sonic Arts, School of Art and Media at Plymouth University, and a musician of repute.  Jane Grant is an artist who works with moving image, sound, installation, drawing and writing. Her work often draws on scientific ideas, both contemporary and historical. She works across disciplines in the arts and sciences often collaborating with scientists, designers and composers.  Together they were commissioned to create a major work for the River Tamar Project, a year-long series of arts events in, on, around and about the River Tamar and designed to bring awareness of its history, current role and future significance to those living on and around it.

 

They came up with Fathom, a site-specific work of sonic art designed to connect people with the river using sound to create an immersive, underwater sound-environment in the grade 1 listed Old Factory Cooperage in Royal William Yard, Plymouth.  Using hydrophones a series of recordings were made out on the river.  These included events that many people would be familiar with, such as the transit of the Torpoint chain-drive ferry which makes a very distinct noise from above, but how many get to hear it from below?  Other sonic events were less familiar – a survey ship making weird hammering sounds, the push-pull of huge pressure changes as a massive Royal Fleet Auxilliary ship is manoeuvred onto a mooring by powerful tugs, and the general soundscape of the waters of the Tamar and Plymouth Sound;  a very lively place below the waves, and in very unexpected ways.  The recordings were to be complemented with live input from a pair of hydrophones delivering a constant picture of the underwater activity throughout an entire weekend.

 

The key element of Fathom that John and Jane wanted to convey however was the divide between water and air, and Jane’s concept was to create a boundary at 1 fathom from the floor (6’6” for you land lubbers) where visitors to the large scale piece could climb steps and emerge from the sonic water into the very different atmosphere above.  This might seem a reasonably simple idea, but the physics of sound and conventional loudspeaker technology just don’t allow for such a sudden cut-off.  They approached me to find a way of achieving this convincingly.  My experience in designing sound systems that put sound where it is required, and as much as possible keep it away from where it is not has seen me attempting to defy the laws of physics on many major concert sites, such as Glastonbury and Reading festivals.  Never before have I been charged with focussing full-frequency sound into such a tight area.

 

Traditionally, control of the dispersion of sound from loudspeakers has been achieved using acoustic devices such as exponential horns, or arrays of transducers in line formats or point source clusters, and whilst these go some way to putting the energy where it is needed, low frequency control is minimal and they would not provide the kind of dramatic boundary that Fathom required.  Modern digital signal processing has afforded more control, but still nowhere near being able to ‘switch off’ sound over a vertical distance of around half a metre, as would be the case for visitors to Fathom as, climbing step ladders, they emerged from a sonic fathom deep into the sonic air.

 

I turned to my friends at Martin Audio in High Wycombe for the answer.  The company has developed a new kind of loudspeaker system that utilises Multi-Cellular Array™ technology to enable an unprecedented degree of control over how a loudspeaker system behaves, primarily with a view to giving audiences a more egalitarian experience wherever they might be at an event.  The system is called MLA, and it has been shaking up the world of concert audio in a big way.

 

The underwater sonic experience would consist of 8 stacks of 5 MLA in a space 30m x 15m, reproducing a one hour loop of material recorded in the waters around Plymouth, mixed with sound from a pair of live hydrophones suspended in the Tamar estuary close to Royal William Yard.  These gave a real-time sense of the changing nature of the aquatic environment as the tides surged and retreated, giving the installation an almost tangible connection to the waters so near yet unseen from within the building.  The air experience would be a ring of six more conventional Martin Audio DD6 loudspeakers on tall stands in the centre of the space, where listeners would climb up steps into a stereo soundscape generated by a pair of DPA 2011 mics rigged over the water where the live hydrophones resided.

 

If I were to be honest, I wasn’t sure how well it was going to work.  The MLA system was being asked to cover no more than about 7m, tail off rapidly and create a hole in the coverage at 6’6” from the floor.  It was really pushing the envelope, and audio quality was not necessarily the highest priority but the sound system optimisation software said it was possible.

 


Above left is a screen shot of the final optimisation that greeted the listening public.  It demonstrates the incredible ability of MLA to really put sound where it’s needed, and if you are interested in teh technology behind this work, I urge you to enlarge it.  Essentially, the yellow and green area is the 1 fathom of underwater sound, and the blue area is above that where the air is heard.  The index plot shows around 8db of reduction between around 60Hz – 250Hz and from there up it all but disappears right at the height of around 1 fathom!  With some heavy lifting equipment, a little acoustic treatment and more time, I believe that this could have been improved on, but whether that was necessary was debatable, as demonstrated by the looks on people’s faces as they climbed the steps into the air – big smiles and nods of understanding all round.

 

Visitors were captivated by the sonic content, some spending the best part of an hour fascinated by the snapping of shrimps and barnacles and the growling of cod (no, really, they do growl like grumpy old men), and a particular highlight would be a passing vessel being heard below the water and above at the same time, followed by the sound of its wash hitting the shore near the live hydrophones.  But beyond that unique experience, many wanted to know about the technology, awed by the spectacle of 40 MLA in a grade 1 listed warehouse.  They were leaning up against the arrays, stroking them and just staring at the stacks, having almost certainly never been that close to a speaker system of that scale.  At least four marine engineers were intrigued to know about how the system achieved the amount of control, and the conversations about how Multi-cellular Array™ technology worked and the parities with submarine listening methods was fascinating.

 

Fathom was the first time I had ever designed a loudspeaker system intending to abuse rather than use its capabilities.  Conventional loudspeakers would not have achieved the desired effect that Jane Grant and John Matthias wanted, and from their own admissions they could never had envisaged it being as effective, had MLA and Multi-cellular Array™ technology not been available.  Fathom was unique not only as an artistic event, but for how it stimulated cross-discipline discussions – sound engineering and listening to whales and submarines, using sound to convey the human impact on an environment that is alien to us, and how art, engineering and technology have become inseparable.

 

Martin Audio made this extraordinary work possible.  Their sponsorship of the event was critical in turning an idea into a sensory experience, a concept into reality. By using MLA the feeling of weight and density that Jane Grant wanted to convey was there the moment you walked into the space, at the same time all the fine detail of minute creatures and water movement was there too, captivating in its unfamiliarity.

 

Fathom can work as art, education, advertising, aquatic evangelism, anything that can be imagined where the oceans are central to people’s lives.  In days where the news of what is going on out there is rarely positive, surely that’s important.

 

share this

categories

archive

© 2017 Simon Honywill

Website design Devon by N9 Design N9 Design We Made This