CREDIT: D. O'CONNELL

Hollywood may soon be able to craft acoustic illusions that sound better than the real thing, say researchers at Brown University.

Technicians, known as Foley artists after Hollywood pioneer Jack Foley, create the noises that populate the soundscapes of radio, film, and television. A crackling fire, for instance, can be evoked by twisting cellophane, and squeezing a box of cornstarch can mimic footsteps in snow.

Because Foley effects often possess very different acoustic properties than their real-life counterparts, psychologists Laurie Heller and Lauren Wolf wanted to find out which components are key in recognizing a sound. First, they had 17 volunteers listen over headphones to familiar sounds, such as breaking glass, paired with Foley imitations. This confirmed that Foley sounds are still not as believable as the real thing.

The researchers then attempted to create sounds that were better than the real ones by digitally manipulating the three most successful Foley effects: "walking in mud" (squishing wet crumpled newspaper), "walking in leaves" (running fingers through cornflakes), and "crushing eggshells" (squeezing folded sandpaper).

More than 70% of the time, listeners rated these new sounds as more convincing than the real ones, the researchers reported last week at the annual Acoustical Society of America meeting in Pittsburgh. They say enhancing the slow-moving wave components of a sound--what is known as its "envelope"--results in a better perception of actions such as walking. But augmenting the fast-traveling sound waves apparently helps people identify materials involved in an event, such as mud.