The salvage yard at M. Maselli & Sons, in Petaluma, California, is made up of six acres of angle irons, block pulleys, doorplates, digging tools, motors, fencing, tubing, reels, spools, and rusted machinery. To the untrained eye, the place is a testament to the enduring power of American detritus, but to Foley artists—craftspeople who create custom sound effects for film, television, and videogames—it’s a trove of potential props. On a recent morning, Shelley Roden and John Roesch, Foley artists who work at Skywalker Sound, the postproduction audio division of Lucasfilm, stood in the parking lot, considering the sonic properties of an enormous industrial hopper. “I’m looking for a resonator, and I need more ka-chunkers,” Roden, who is blond and in her late forties, said. A lazy Susan was also on…