In her latest column from Shetland, Jennifer Lucy Allan familiarises herself with Sumburgh Lighthouse’s foghorn

On the Monday of my second week in the lighthouse, Brian Johnson, the retained keeper, comes to switch on the foghorn on for me. It is what I am here to write about (I am doing a PhD on foghorns) and I am extremely excited, not least because I have barely spoken to anyone in over a week.

Sumburgh Head’s old siren foghorn was restored in 2015 (all Scottish foghorns were switched off by 2005) as part of the renovations here. It is a squat circular whitewashed tower, perched about as close to the edge of the land as it is possible to be without actually being in the sea. The lighthouse station’s perimeter wall protects against the sheer drop, and on the cliffs below seabirds huddle, chattering between themselves in pairs on tiny ledges. The long tomato-red trumpet reaches over the drop, a gaping mouth pointing out to sea braced on matching red supports.

Foghorns require a lot of equipment: as well as the trumpet, and the building that holds up the horn, there are three diesel engines (one of which is a backup) that take ten minutes to warm up, in a building next to one of the old keeper’s accommodations. The engine room smells like diesel, brass polish, greased metal and sticky gloss paint. The floor is tiled in an ochre and terracotta pattern, an ivy frieze painted around the wall in cream and green gloss paint.

The engines start on a dinky capful of petrol that gets them moving, a spluttering rattle before they start turning over with a chug-chug-chug. When this happens Brian opens the valves and turns a lever. From here the engines pick up to a clunking canter, a steady post-punk four-four, loud enough to have to shout over and still not make out the words of the person standing next to you. Then the air-valves are opened by turning wheels that open pipes into the massive braced and bolted cream receiver tanks that line one side of the room. From these, the air passes through underground pipes up to the trumpet, where Brian opens another valve that lets it into the siren.

Up the spiral stairs inside the foghorn building I stand next to the narrow opening at the neck of the trumpet, inside which is a siren that’s getting ready to scream. A clockwork mechanism on the wall, all green paint and brass cogs, clicks through a 90-second sequence, a flat raised section of cog indicating the honk. It clunks into place and a whizzing sound surges as the siren hits 1200RPM, and then – fingers in ears! – the foghorn blasts. From next to the horn the seven full seconds makes my guts buzz and ears hum, a terrific yell of a sound.

It becomes a party to our conversation: we both pause in mid-air as the siren parps, then continue as if nothing happened. People emerge from offices I didn’t know were here. There are some engineers in from the Northern Lighthouse Board fixing something to do with the radio masts and they gather under the horn. One calls his boss in Edinburgh and his girlfriend, to let the sound play down the phone. As the sound fades one giggles, made giddy by the sound. Someone who came up to have a look at the lighthouse looks on, bemused at this impromptu engineering ritual. I sprint around the site in the spaces between soundings, across muddy squares of turf and into the ruined radar hut, trying to find a spot  to record that is sheltered from the buffeting winds.

I used to think this was a lonely sound, a big melancholic beast echoing into the vastness of the open sea, often to nobody at all. But it isn’t. This heaving machine is the sound of someone else, the sound of civilisation, of safety, regularity and rhythm. I love this sound – comedic up close and comforting from a distance.

Perhaps it is because staring into open sea induces a pure horror in me. Leaning against the wall directly underneath the horn I can hear the sound echoing into this open landscape like a skipping stone, bouncing off invisible air currents and the surface of the water. If I really stare, force my gaze to take in the blue-grey panorama from the edge of the land, an animal panic sets in and I have to turn, gulp in some people, buildings, some scenery with scale. As I stand at the edge I realise that with each sounding of the horn, my fear of this open seascape lifts. In the 90-second gap a feeling of exposure and insignificance rises like blood to the head, the smallness of my human body against the enormousness of the sea a deeper, more sublime terror than anything I have experienced inland.

Off the coast here, between me and Fair Isle to the south west, there is a patch of water called the Sumburgh Roost, its old Nordic name referring to a ‘thunderous noise’, caused by two currents jostling together. In a 1951 article on seas and moons for the New Yorker, Rachel Carson quotes the British Islands Pilot, which describes it as a “confused, tumbling, and bursting sea” where “vessels often become entirely unmanageable and sometimes founder, while others have been tossed about for days together”. I had thought about catching the once weekly ferry to Fair Isle, but I am warned off, the roost guaranteeing a horrible crossing. There is a line of breakers off Horse Island to the west, which could be the roost. It looks too close, but my perspective is warped by the distance and lack of detail.

It doesn’t take much open sea to make one feel insignificant. 300 feet above the puckered indigo surface, the horizon is a very long way away. This view is not empty, nor is it relaxing. “The sea’s instinct collaborates with ours to create thinking,” writes Etel Adnan, and this is a huge stage upon which the teeming, roaring chatter of my mind can roam freely, a cacophony only I can hear, that spreads itself across a blue canvas all the way to the dark band of the horizon.

But stood under the foghorn as it sounds, I am sheltered, tucked in under an engineering monster that is bigger and stronger than me, that has stood for a good century or so since being dragged to the top this inhospitable headland. As the siren whirrs its warning warm-up again, I shut my eyes against the view and wait for the blast, for my internal chatter to be briefly silenced by compressed air, by a machine that is bigger than me and can shout loud enough into the void to scare off my own demons lurking under the brooding surface of the water.