The sweet science of punch sound effects bears little connection to reality:
For the gritty “Out of the Furnace,” released in December, the film’s sound-effects designers wanted Casey Affleck’s brutal fist fights to have visceral, fist-on-flesh punch sounds. They recorded a martial artist pounding on human flesh but also had him punch blobs of pizza dough, a slab of beef with a wet towel on it, a watermelon, and—to simulate the sound of bones cracking—dry pasta shells.
In the boxing comedy “Grudge Match,” released on Christmas Day, punches between Robert De Niro and Sylvester Stallone contain recordings of real boxers hitting each other in a gym. But decisive blows in the big fight scene are punctuated with the bang of a kick drum. And slow-motion super-punches include audio of a howitzer cannon blast and a prison door slamming, recordings that the film’s supervising sound editor Terry Rodman made years earlier for other purposes.
Punch sounds are always added after filming, of course, because the actors aren’t really hitting each other. Early filmmakers felt that the genuine sound of a fist hitting a face was too dull to match its visual excitement. So sound professionals invented more thrilling, phony punch sounds to dub in—audio effects that came to be known in the trade as “the Hollywood punch” or the “John Wayne chin sock.” Hams were slapped, belts whipped. In an old Western, an outlaw getting slugged might be accompanied by a recording of billiard balls clacking. For kung fu movies, bamboo stalks were whacked on boards.
“The sound of a punch that we’re familiar with is not made with any punching. It’s a wet towel slapping on a wall, sometimes with a pencil breaking added in there,” says Leslie Shatz, who worked on “Out of the Furnace.”