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 video games-it’s a trove of potential props. 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.