Sound designer Robert Mackenzie started working fairly early on during the editing of Hacksaw Ridge, the true story of conscientious objector Desmond Doss (Andrew Garfield) and his heroism at the Battle of Okinawa. The picture department needed battle sounds, especially since director Mel Gibson wanted to determine if the first battle sequence would play emotionally with just sound effects and no music.
Finding the correct tone was the biggest challenge Mackenzie faced in the sound design. He needed to discover “what the picture demanded.” It was necessary for the sound to be both heightened and emotional.
“Mel was very specific about what he wanted the sound to do. It’s very brutal. It’s very realistic. It’s quite emotional to be in the middle of the battle,” shared Mackenzie. “It’s not an action movie. It’s not a documentary. It’s finding the sounds that make it realistic, but brutal at the same time.”
There was some experimentation to find the right sounds. A combination of recorded and library tracks were used. Mackenzie started from an authentic base, using authentic, period weapons. Adding a layer of authenticity, post sound used tracks recorded by the production sound mixer because real explosions and box bombs were used on set.
“Sometimes the accurate sounds that you record are unimpressive, to say the least,” commented Mackenzie. “We manipulated the recordings to suit each particular scene and what’s going on in the scene. Sometimes you want the guns to sound big and impressive and dangerous. We had the American guns sounding big and heavy, with a lot of artillery and power behind them. Sometimes you want them to sound accurate and smaller and more precise. In the case of the Japanese guns, accurate stealth, deadly accuracy.”
The team tried to eschew too much layering in order to a avoid having the effects sound like designed effects. They wanted the audience to engage and completely believe the audio was real, but have the audio be emotionally powerful as well.
Gibson wanted the sound to have high impact in contrast to Dosh’s pacifist stand. He wanted to depict the horror of war, show it for what it is, raw brutality. The portrayal was so violent that it was sometimes hard for the crew to watch footage over and over again.
“Soldiers never get over it. That was something Mel wanted to bring to the picture, the fact that they guys never get over it. They are scarred for life with post-traumatic stress. They are never the same again,” revealed Mackenzie. “Mel actually had some veterans come in to watch the mix while we were working on it to check the authenticity in what we were doing, to make sure we were truly representing what they had experienced right in the thick of it.”
The veterans commented that the bullets whizzing and cracking overhead really did sound like that when they were down in the bunkers and foxholes. They were affected by the film’s realism.
War footage was not the only design consideration in the film, which opens in the peaceful Blue Ridge Mountains. To contrast the two worlds and keep from telegraphing the battles to come, the design for Dosh’s boyhood home was made as idyllic as possible, almost like a separate film. One of the main challenges in the Virginia sequences was that they were filmed outside of Sydney, Australia.
“Being Australian, one of our sound editors took a trip to that area in the States,” explained Mackenzie. “In the dialog tracks there were kookaburras and all sorts of Australian wildlife. We had to remove all of that in between words and ADR the birds we couldn’t get rid of, because that was a dead giveaway hearing a kookaburra.”
Because sound is such a team effort that takes so many people and so many different talents to bring it all together, the thing that Mackenzie is most proud of is his crew and their contributions to the audio landscape that they created together.