'Hacksaw Ridge' sound mixer Kevin O'Connell explains his craft

Meet the sound mixer of "Hacksaw Ridge" who has been nominated 21 times.

— -- During movie awards season, a lot of attention is given to the Oscar-nominated actors and directors.

But what about the nominees whose job responsibilities aren't quite so obvious to the average moviegoer?

For a new series called "Behind the Lens," ABC News got to know the people who were recognized for work behind the camera.

"Hacksaw Ridge" sound mixer Kevin O'Connell knows that a lot of people have no idea what his job entails.

However, he noted, his fingerprints are on every scene in the war film.

That's because, in general, a sound mixer's responsibility is to make create "the sonic landscape" of the movie, mirroring how a cinematographer determines its overall look. Every sound in "Hacksaw Ridge" was replaced, amplified or polished, and it was the responsibility of McConnell and his team to ensure that each one sounded exactly right and stirred emotion.

"What a lot of people don't understand about what we do is that when they shoot the battle scenes, it's a bunch of guys running around, basically, a dirt field the size of a football field and all of the explosions are props, the guns are props, none of it makes the noises that it does," he told ABC News. "The only parts of the original tracks that we were able to keep were very small pieces of the dialogue. Other than that, every single explosion, gunshot, ricochet, bullet whizzing sound, footstep, everything has been recreated with period authentic weaponry to create what was essentially the Battle of Okinawa."

To stitch the film together, O'Connell and his colleagues worked for months at studios in Australia and California, poring over a mixing console filled with thousands of sound effects ranging from dialogue to the music played by each section of the orchestra. O'Connell also gushed about the newly-updated sound system that has become more commonplace in movie theaters, which is comprised of many speakers strategically placed around the room. The possibility of better surround sound allowed the "Hacksaw Ridge" sound mixers to create the audio illusion of bullets whizzing overhead while explosions blasted in the periphery.

"Most people think it’s sort of a technical thing, but it’s really not," he said. "It’s a very artistic craft."

"He hires people that he feels are competent to do the job and then he lets you do what you do," O'Connell said. "He puts his heart and soul into everything he does. He's an emotional director and so when the scene calls for a particular emotion he knows exactly what he wants to get out of that."

"You couldn't have a better film for sound than 'Hacksaw Ridge,'" he said. "It epitomizes what the sound award is all about."