By Melody Lau
Did you feel nauseous watching Christopher Nolan's latest war epic, Dunkirk? Well there's a really good reason for that. Aside from the intense sounds of bullets and explosions, and up-close POV shots of pilots in the air and soldiers struggling underwater, Nolan's secret weapon in this retelling of a crucial moment in British history was a sound effect called the Shepard tone.
The Shepard tone, named after American scientist Roger Shepard, is a sound created by stacking sine waves that are an octave apart and moving the bass note upward or downward. The result is a sonic loop that appears to rise or fall in pitch, but never actually does — an endless scale that has been proven to cause headaches and nausea.
It's an important part of German composer Hans Zimmer's score for Dunkirk, but he admits the idea originated with Nolan. "Chris had written the script for Dunkirk in a musical shape," he explains. "So, to be honest, I didn't really have a choice here because he had already designed the film very much with the music in mind."
In addition to that, Nolan provided Zimmer with the sound of a ticking watch — a recording Nolan made of a watch he personally owned — to embed into the music. The result, as heard throughout the film, was a heightened experience that left audiences tense and fearful, as if viewers were on the beach alongside the soldiers, uncertain and anxious of their fates.
If you look back at many of Nolan and Zimmer's other collaborations throughout the years, including the Dark Knight trilogy and 2014's Interstellar, the Shepard tone is present in those scores as well. So why are Nolan and Zimmer so obsessed with this auditory trick?
"It's the idea of eternity and endlessness," Zimmer reveals. "It's the idea of playing a trick on time itself." It's a point that makes even more sense in films such as Dunkirk, Interstellar and 2010's Inception, all of which play around with the idea or structure of time, whether it's displaying different timelines, morphing the speed of time in space travel or slowing down time as you dive into the subconscious.
Zimmer goes on to tease some secrets to the music of Dunkirk that he says he won't be disclosing any time soon: "There are a couple of things we did in the movie which we want to just keep secret, you know?"
His reason for not sharing, though, is because he wants to maintain a specific kind of thrill for moviegoers. He adds, "If I open the curtain and I let you see all the insides of the machine, it's not going to be quite the same thing. Dunkirk is more of an experience than it is a movie."