The eerie racket fills the room, getting louder and louder as Peter Scally, in his Second World War khaki army uniform, cranks its handle. Faster and faster he turns, louder and louder becomes the siren, drowning out the children's giggles and forcing the women in the office downstairs to shout into their desk phones.
Finally the wailing drifts away and as Craigroyston's two primary seven classes settle down, Peter explains to youngsters several generations removed from the horrors of the Second World War what they just heard.
He talks of Anderson Shelters and families emerging to find homes and streets flattened, of Nazi bombing raids and the Home Guard brandishing sticks shaped like rifles and guns without ammo, of meagre sweetie rations, of evacuation, digging for victory and daredevil spies with knives sewn into their collars and string vests that could unravel to produce a length of rope.
Behind him a table heaves with his personal collection of wartime odds and ends - everything from US "pineapple" hand grenades which he casually chucks towards the girls in the front row inducing a flurry of squeals, and rifles that all the boys are itching to hold.
There are maps printed on silk scarves, daggers made for concealing up a sleeve and even a bit of Great War shrapnel which was removed from his own grandfather's back. He's bringing history to life for a modern generation. But it's a lesson in the reality of war that's even more poignant and provocative because of where it's taking place.
Along a corridor and down some stairs from the boardroom is the factory which every year churns out Scotland's five million plus remembrance poppies.
Each is individually made by an ex-servicemen, some still mentally traumatised years later by what they've witnessed, some carrying physical injuries that have left them struggling to support their families in any other job.
Around 40 work at the Warriston Road factory, each behind their own individually-decorated work station - usually regimental colours apply - with a wooden block in front of them on which to rest each green plastic stem, its papery red petal shape and then the small black centrepiece.
On an average day, explains Andy Corbett, 48, of East Craigs, he can churn out a staggering 3500 poppies. The former Royal Highland Fusiliers' signalman and veteran of the Troubles in Northern Ireland holds out his hands to show off the calluses that prove it.
The work is, he says, repetitive and, if it wasn't for the friendly banter and jibes that endlessly ricochet around the room, achingly dull. What livens things up, he adds, are the children.
Around 1300 visit the factory during a three-week period around Remembrance Sunday, to hear war historian Peter and his ear-piercing siren, to try on his collection of tin hats, helmets, khaki jackets and pick up a hand grenade or two.
Today's it's Craigroyston Primary's turn. Two of the pupils, Emily McDonald and Nathan McManus, both 11, have been dressed by Peter in typical Second World War soldiers' gear, their shoulders slumped under the weight of their kit.
"It's heavy," says Nathan, groaning. "Come on," yells Peter, grinning and throwing on an extra backpack. "You're a soldier. You're tough. So tough you don't even take milk with your cornflakes!"
The two P7 classes collapse in giggles. Moments later, though, their mood becomes more thoughtful as they file downstairs to learn how the simple poppy emblem helps a new generation of fighting forces cope with the aftermath of battle.
They meet Tom McPhillips, 65, from Stockbridge. He's the factory's tour guide, a former Royal Signalman whose grandfather died at Ypres, who served himself in Aden and whose nephew was George Medal holder Gary O'Donnell, the brave bomb disposal expert from Edinburgh who was killed in Helmand province in 2008.
Tom came to the factory six years ago having realised he was losing the battle to cope after his wife's death from cancer. The factory gave him a reason to get out of bed each morning - today it's giving him further purpose, as he sets about showing young people the importance of remembrance.
As Erin Milligan, 11, and her Craigroyston classmates settle down to make some poppies, he points out a wall at the heart of the factory floor. It is covered with handwritten letters by children from an earlier visit, some simply saying "thank you", others elaborately decorated with drawings of poppies, many with carefully-crafted verses summing up what they imagine to be the horror of the battlefield.
"They're very moving to read," he says. "They're just children, but they sum things up brilliantly. Sometimes their letters can actually move the guys to tears."
The factory visits are one element of the work being done by Poppyscotland to teach schoolchildren about veterans, remembrance and conflict.
It recently launched a new educational package of learning materials designed to fit in with schools' Curriculum for Excellence, which includes a 20-minute film featuring a group of six Dunbar Grammar School pupils during a visit to First World War battlefields in Belgium and Northern France.
There are others who could perhaps benefit from such materials, especially as the poppy has, for some, become a controversial emblem. Indeed just last weekend a section of Celtic fans brandished a banner declaiming the wearing of the poppy - a stance from which the club quickly distanced itself, with promises to ban the individuals responsible.
Poppyscotland chief executive Ian McGregor says: "We are very proud of our education project. In order for Poppyscotland to continue its work in the future it is vital that as they grow up young people have an understanding of the difficult and demanding issues that war and remembrance raise."
For Craigroyston Primary School's boys and girls, all of them from the Muirhouse area, simply leaving the classrooms to see what goes on at the factory walls has had an impact.
Cameron Mackay, 11, has been mesmerised by Peter Scally's collection of hand grenades since he arrived. Now he's getting to hold one, turning it over in his hands, fascinated by the potential power that would have been encased in its tiny shell.
"I like the hand grenades. And the spy stuff - that's cool," he says, referring to a mannequin propped on Peter's table with a biodegradable parachute helmet, that vest that unravels to produce 30ft of rope and a fold away dagger easily concealed in a sleeve.
"We've been learning about the Second World War in school, but this makes it more real and easier to remember. It makes me feel sad too that people had to die and that there had to be a war at all."
The school's principal teacher Peter Mackay says the visit helps bring history to life. "The children have been learning about the home front and selling poppies, so this ties in with their class work.
"There's only so much you can tell children and there can be aspects that they just don't connect with.
"It's why it's wonderful that they can come and see things for themselves."
For details of Poppyscotland's work and appeal, go to www.poppyscotland.org.uk
THE Lady Haig Poppy Factory makes Scotland's five million-plus poppies and 8500 wreaths every year.
Demand for the poppy products is growing, according to factory manager Major Charlie Pelling, who served with the Royal Tank Regiment.
"We are selling more wreaths than ever. The poppy is such a simple, powerful emblem that says it all."
There has been a poppy factory in Edinburgh since 1926.
Last year sales of the poppy in Scotland raised 2.2m for PoppyScotland.