Pristine and perfect, for visitors who travel past the calm sanctuary of Iona Abbey to reach the island’s North End beach find a precious place on earth, seemingly far from the turmoil and turbulence of the modern world.

When a lone whale washed up on an August day in 2018, it seemed to be just an unfortunate act of nature, the sort that has ignited curiosity and excitement among islanders for generations.

Some arrived to collect bits of bone as souvenirs: in days gone by this unexpected gift from the deep would have provided oil, been turned into disinfectant, ointments, tar even food and medicine.

However, this whale - a Cuvier's Beaked whale with the species’ distinctive ‘Joker’ smile – was more than a single, unfortunate one-off.

At beaches across the Hebrides that August, on shores in Ireland, Iceland and the Faroe Islands, almost 120 whales lay dead.

With no obvious indication of disease, the possibility of mid range military sonar being the cause of the mass mortality was considered by investigating scientists.

The episode brought into sharp focus the delicate balance between the military exercises that take place not far from the peaceful beauty of Hebridean beaches, and the fragile creatures – from whales to even plankton - affected by their movements.

Iona-based artist Mhairi Killin witnessed the excitement as news of the whale spread and anguish as it became clear it was just one of many.

With no evidence of illness to be found, marine specialists suggested the whales may have become disorientated by high-powered military sonar being used by vessels taking part in a major exercise in the area at the time.

Driven to explore the episode further, Mhairi spent eleven days at sea on board the Hebridean Whale and Dolphin Trust research boat Silurian during last May’s NATO Joint Warrior Military Exercise, joining scientists as they monitored its impact on sea life.

During the journey - which ranged from The Sea of Hebrides up to Cape Wrath and involved gruelling ten-hour work days in often challenging weather conditions - Mhairi and HWDT scientist, Becky Dudley collected sound and visual data using hydrophones and computer software.

The result of her investigations is a multi-layered series of artworks that interrogate the power and reliance on sound as a survival tool for the creatures of the deep, and the impact upon them of military activities carried out in the name of national security.

At its heart is a poignant multimedia exhibition featuring sculpture made from the bone of one of the dead whales, and a collaborative fusion of video, music and poetry, aimed at igniting debate around the difficult balance between the use of military sonar and the creatures who rely on their incredible senses to navigate, feed, breed and survive.

Alongside the physical installation will be a podcast series in which Mhairi talks with scientists from the Hebridean Whale and Dolphin Trust and Scottish Marine Animal Strandings Scheme, as well as islanders and creatives who have been involved in the project.

One of the most arresting elements of the installation, On Sonorous Seas, will be the remains of a Cuiver’s Beaked whale washed up at Bragar on the Isle of Lewis during the 2018 episode which saw dead whales scattered on beaches across a vast area.

Its skull will be suspended above a reflective floor as part of a sea and star map. Created in collaboration with artist Tom deMajo from Biome Collective, it shows locations of the dead whales and reflects Cetus, the whale constellation.

It will be accompanied by a poignant soundscape created almost entirely from hydrophone recordings of orca calls, dolphin clicks and whistles, magnified sonar and boat engines made during the research trip on the Silurian.

Mass strandings of whales have become a significant issue in recent years, with scientists pointing to the sonar used to trace submarines leaving the creatures disorientated and frightened.

Stress and fear prompt the whales to rise to the water’s surface too quickly. As a result, they suffer decompression sickness, similar to ‘the bends’ which can be fatal for divers.

It’s thought Cuvier's Beaked whales – are particularly susceptible. With a cone-shaped head and stubby beak, they typically live at depths of more than 300m and make long, deep dives in search of squid, surfacing only briefly to breathe.

Over 45 badly decomposed Cuvier’s Beaked whales washed up on the shores of several Hebridean islands, including Mhairi’s home of Iona, during the 2018 episode.

A further 23 were stranded on the west coast of Ireland, with more found scattered on the coast of Iceland and the Faroe Islands.

Scientists probing the event, said to be one of the worst of its kind, focused on the Porcupine Bank area off the west coast of Ireland and the increased presence of military sonar in the area at the time.

While the Ministry of Defence initially denied that Royal Navy operations were involved, last September it vessels were operational in the area at the time, and acknowledged the risks to marine life from active sonar.

Mhairi said the exhibition highlights the difficult balance between national security and nature.

“It’s very complex - people value national security and people also value the ecology and beauty of the oceans.

“Scientists know very little about the environment and behaviour of the deep diving whales and we know nothing about what the military is doing.

“By transforming how we tell the narrative of the 2018 mass standing of 118 beaked whales - a narrative embedded in the overlay of two cryptic environments, the habitats of the military and the habitats of the whales – through a partnership of science, music and art, we transform how we observe this story, and perhaps in doing so we can tell reality differently and bring an audience towards the complexity of this issue.”

She was on Iona when word spread across the island of a dead whale found on North End beach, known for its crisp, white sands and glorious views.

“A bit like historically when a whale came ashore to an island, there was a buzz,” she says. “Historically it would be a source of food, oil and whalebone. Similarly, when this carcase came ashore in Iona word got around the island quite quickly.

“The whale started to disappear and diminish - people were acquiring parts of it. Elements of the spine were taken and the skull was removed. There was a huge amount of curiosity about it, and that fascinated me.”

Cultural attitudes and practices around whales found beached and stranded form part of the podcast which will accompany the exhibition.

Mhairi, whose previous work, Fata Morgana, explored the issues created by military waste, worked with musician Fergus Hall to create the soundscape. Elements will be performed at locations where the Cuvier’s beaked whales stranded, on Mull and Iona, with talks by the artists and scientists involved in the project.

The work also features a poem written by Dutch-born and Mull-based poet and artist Miek Zwamborn as an elegy and requiem for the whales, and calligraphy by artist Susie Leiper on loose leaf papers imprinted with impressions of whale bones gathered during the stranding event.

On Sonorous Seas is at An Tobar on Mull from 8 July until August 27.