When the silence recovers its composure, it does so with authority. It seems to wash over everything – the surrounding mountains, the patches of scrub on the ridges, the boulders that cling to unlikely gradients. I close my eyes, try to pick out a sound. There is nothing.
Of course, there is a chance that my ears are still adjusting to the sudden shift in volume.
Six minutes earlier, I was in the process of being deafened, the blades of the helicopter howling even as I stood on the scales by the terminal, having my weight checked ahead of the flight. Then we were clambering aboard, four of us in the belly of this metal vulture, headphones and lip-microphones affixed, allowing us to speak amid the roar.
The noise increased as we leapt from the ground, Cline River Heliport diminishing, the shape of Abraham Lake – a crooked, beckoning finger – becoming more identifiable as we rose. Within seconds, the only witnesses to our progress were several bighorn sheep, looking on aghast from a lushly grassed slope.
They too fell away as we soared onward – fir trees a blur of green – before dropping on to a clearing flat enough to enable the helicopter to land.
This contrast between calm and clamour is all part of the plan. The disappearance of the latter – which fades as the chopper picks up its feet and returns to the valley – is a hint that I am now, along with my fellow adventurers, "lost" in the wilderness.
But we are here to escape – and we will do so by hiking along sparse trails, breathing the clear air of lofty altitude, and indulging in a spot of yoga in a section of the Canadian Rockies that guards its privacy. Were it not for the helicopter, the only way to reach this high outcrop would be a day of sweat and toil, climbing ropes slung across shoulders, blisters on weary soles.
The remoteness of our location is instantly obvious. We are perched 2,195m (7,200ft) up on a crag that sits in the V-shaped intersection of two waterways. On one side, Cline River Canyon ploughs a north-westerly furrow. On the other, Coral Creek Canyon claws a route west, slicing through rock towards the spine of North America's most iconic mountain range.
Here, especially, the cloud-scraping drama of the Rockies deserves applause. Yet there is no one here to clap but us. It is 30 miles west to the fabled Icefields Parkway, where the motorhomes of myriad holidaymakers chase road-trip nirvana, lolloping past the slow-flickering tongues of ancient glaciers.
It is 100 miles east to Red Deer, where "civilisation" re-emerges in this dormitory town between Calgary and Edmonton (the two key cities of Alberta). Give or take the occasional soaring eagle or wandering bear, we are on our own.
And we need to start moving. Though this is summer, a chill hangs on the breeze, and the ghost of winter waits by some of the paths, haunting the scene in stubborn dabs of white.
So we begin walking, heading loosely back towards Abraham Lake. In parts, the going is easy. In others, the terrain kicks up, causing calf muscles to complain. Elsewhere, the land plunges and I find myself staring into the abyss, frozen above a descent of giddy depth.
After an hour at a fair pace, we push through a cluster of bushes and onto the Wedding Knoll. Its name is a clue to its personality. Blessed with a 360-degree panorama, it is used by Cline River Heliport as a setting for marital occasions.
The same characteristics – a direct line of sight across to a phalanx of mountain shards opposite, peaks clustered like a colossal coxcomb; the sky wide and epic – make it an ideal site for a little group exercise.
I am a long way from being an expert at yoga. But against such a backdrop, there is a quiet thrill to slipping off my boots, unrolling a mat and drifting again into hilltop silence.
At one corner of the square into which we form ourselves, Martha McCallum, the leader of our band, has rather more knowledge of this peaceful discipline.
A yoga practitioner for more than 20 years, she has been staging these helicopter-powered forays into the upper realms of the Rockies since 2008. In an earlier existence, she ran a café in Canmore, a ski town just outside Banff National Park. It is not difficult to grasp why she fled from the kitchen.
"Breathe in. Let yourself sink into your surroundings. Look around. Take in the beauty,' she says, running us through a series of poses that stretch sense and sinew: the arched back of Downward-Facing Dog; the bowed head of Dolphin; the upthrust arms of Warrior I. Despite my relative unfamiliarity with these movements, I find myself subscribing to the situation.
Through the mat, I can feel the mossy softness – seasoned with the odd pebble – of the ground below my toes. Dashes of sound that were hidden in the aftermath of the flight are now perceptible: the murmur of water on the edge of the clearing; the rustle of an unseen animal, rooting in undergrowth; the faint cry of wind, flowing around the peak.
It is an eventual wrench to break out of this reverie. But there is food to be eaten. Packed lunches – prepared by our hostess, a nod to her catering days – are handed out. There are meaty sandwiches and sticky flapjacks, boxes of salad and piles of fruit. A healthy feast.
As we are chewing, a jet's vapour trail gouges the firmament. The aircraft is invisible, but given the context, this seems a gross interruption – a burglar alarm at 4am; a mobile phone in a library; a coughing fit during a ballet performance. Yet it is also a reminder that the cord has not been cut. One call on Martha's radio will summon the helicopter. Sure enough, it bursts forth at her order, audible long before it is present. And despite the fact that the alternative – a complex trek downwards – is unpalatable, I am sorry to see the taxi arrive.
Martha's Heli-Hikes, Cline River Heliport, Highway 11 (001 403 609 0824; marthashelihikes.com). The "Soaring Spirit Heli-Yoga" package costs from C$429 (£268) per person, and is available from May to September.
Timeless Travel (0844 809 4299; timelesstravel.co.uk) offers an eight-night "Timeless Alberta" road-trip package that involves a drive from Banff to Jasper along the Icefields Parkway. From £1,460 per person, including flights, accommodation and car hire.
Baker Creek Mountain Lodge, Bow Valley Parkway (001 403 522 3761; bakercreek.com). Doubles from C$165 (£103), room only.
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