When director Jonathan Glazer first pitched Johnnie Burn his dramatic vision for The Zone of Interest, the sound designer took a deep breath. Over the past two decades, the pair had developed a strong rapport, collaborating on a variety of commercials, music videos and long-gestating movies (most recently, 2013’s Under the Skin), experiences Burn remembers taking a physical and mental toll on him. But this rigorous new project—a Holocaust drama in which hellish audio is layered over otherwise idyllic imagery—promised to be the most challenging, counterintuitive and audacious job of his career. 

“To be honest,” Burn says, “I was really scared.”

In some ways, Glazer had asked Burn to make an entirely different movie from the one he’d written and planned to shoot—about an Auschwitz commandant, Rudolf (Christian Friedel), his wife Hedwig (Sandra Hüller) and their several children, living in tranquility beside the notorious extermination camp. Depicted with a detached, almost surveillance-style camera, the story follows the family’s life and routines inside their bourgeois home, which boasts a pool, greenhouse and spacious, lush garden. Throughout the year, the kids spend time playing in their rooms or picnicking and canoeing at a river nearby, while Hedwig keeps up with her chores and monitors the home’s hired servants. 

Outside of dark smoke billowing from distant chimneys, Glazer’s depiction is one of domestic bliss. But turn up the volume next door and that impression shatters. Never wanting to show the atrocities occurring inside the camp, Glazer requested that Burn overwhelm and contradict his picturesque foreground with a haunting, unrelenting ambient soundscape, filled with terrifying dog barks, muted gun shots, prisoners’ screams and the incessant, churning rumble of the crematorium. For this family, the death and destruction that wafts over the barbed-wire wall has become another type of white noise. “The point is,” Burn says, “they’re ignoring it.” 

To insinuate genocide sonically, Burn began researching “everything about the sounds that were in Auschwitz in that period,” he says. Over the course of a year, he pored through Holocaust literature, descriptive illustrations and witness statements with details about prisoner treatment and guard harassment. He also built a large map of the camp to know where the majority of executions took place in relation to the family home so he could represent the right kinds of gunshot echoes. Everything then went inside an audio “bible,” a 600-page PDF that listed all the sounds that would have been heard throughout the Polish countryside and within the camp walls. 

“Knowing that there’s such responsibility with the sounds that we’re using and knowing what an enormously rigorous filmmaker Jonathan is, he wouldn’t want anything other than to be absolutely correct,” Burn says. “Everything had to be done to the highest degree of recreation.”

Along the Sola River, sound mixer Tom Willers brought his boom mic to capture the summertime sounds of native frogs, birds and insects; later, without the luxury of boom mics, he hid microphones around the house to capture dialogue. Around the camp walls, however, Burn devoted himself to further historical and geographic accuracy, collecting audio of people walking across gravel in parking lots with Polish clogs, or visiting Paris, where he took a team out at night to gather the echoing shouts of French men that might realistically portray a prisoner riot. “Normally, you would always want to record foley [noise] somewhere really quiet with no echo,” Burn says. “But here, it was really important to feel the space, because that really helps the imagery that you’re drawing in your head.”

In a scene in which Rudolf castigates a prisoner for stealing apples, for example, Burn recorded Friedel atop his horse on a hard platform to ricochet and soften the noise of his attacks and insults. “It’s difficult for any actor to sound in severe pain or threatened without getting themselves into a very difficult headspace,” Burn says. As a result, the bulk of his work felt like directing his own film shoot, which required multiple locations that could reflect the varying degrees of noise entering through the family home’s windows and its guarded gates. “You have to go and do it for real in order for it to sound as credible and good as it does in that scenario,” he says. 

The most visceral sound of the movie, however, is the camp’s constant mechanical din, a combination of bustling prisoner workshops and a growling furnace that accentuates the family’s mental separation from their landscape. Burn established the sound early into Glazer’s first cut, after the director asked him to mimic a funny noise that actor Luis Noah Witte had made with his mouth during a bedroom scene. Soon, Burn began blowing on microphones, trying to copy Witte’s rhythm, before supplementing it with a recording of a chimney on a windy day, all of which “basically sounded like flames,” Burn says. The only problem? The spare, fiery sound didn’t reverberate with much menace. 

After an early test screening that Burn describes as “underwhelming,” production designer Chris Oddy approached him and Glazer and suggested that the camp’s low hum sound more industrial. “It needs to be way more comprehensive,” Oddy said. “Millions of people went through here.” Burn agreed, believing he and Glazer had missed the mark by being too cautious in their design. Initially, he thought about recording an industrial incinerator along England’s south coast, but its sanitized, high-pitched whine wasn’t representative of the technology 80 years earlier. Instead, back in the studio, Burn took the same file and slowed it down, layered and thickened it, and gave it a “bassy rumble” by removing the treble. 

“We were putting it on that shot, and [Glazer] said, ‘Why don’t you just try it on the whole film?’” Burn remembers. “We did that, and it was just remarkable. It’s this constant reminder that is the whole premise of the film.”

The more omnipresent, haunting sound fit nicely into Mica Levi’s similarly unsettling score, which accents Glazer’s abstract flourishes and end credits. Though they and Burn never explicitly collaborated together, each often checked in with the other’s progress and helped solve their creative problems. “I’m crafting a wooden chair here, and Mica is next door doing the table that goes with it,” Burn says. Though Levi wrote more music for the first half of the movie, Glazer and Burn both felt anything beyond the ongoing rumble might give off an artificiality that would undercut the movie’s horror. “It’s the most absolute version of the truth of what happened then,” Burn says, “and we wouldn’t have got there without having listened to Mica’s music.”

Throughout the final mix, which took place at post-production studio Halo in London, Burn and Glazer worked hand in hand, sharpening and refining their “work as they go” process that, throughout the shoot, helped them determine whether a scene was working. Most important, they funneled their Dolby Atmos sound into a mono output, believing the technology’s more immersive, spatial qualities sounded too sensationalized. “It just made it feel more like a document than anything else,” Burn says. “It stopped there being a glossiness about the way the sound was presented.” 

Upon The Zone of Interest’s premiere at Cannes last May, Burn caught viral meningitis and needed to stay in the hospital for a few days, an example, he says, of his body’s physical and emotional exhaustion working with such heavy subject matter. “I definitely turned around to my wife about three weeks in and said, ‘I think I’m getting depressed,’” he says. Though the five-year experience, he says, was ultimately rewarding, it was hard to shake the soul-crushing and burdensome work of accurately representing inhumane violence every day. “I mean, it was awful,” he says, before offering a semi-serious suggestion: “I would not advise anyone immersing themselves in this material for that period of time.”