That sounds about right

A new study by researcher Laurie Heller supports longtime claims by sound effect technicians, known as Foley artists, that exaggerating sounds in movies makes the sounds more believable to the audience.

by Kristen Cole

The sound that accompanies an onscreen image of feet sloshing through mud is an exaggeration of the true sound, but viewers don’t mind. In fact, we may think it is more realistic that way.

A new study by researcher Laurie Heller supports longtime claims by sound effect technicians, known as Foley artists, that exaggerating sounds in movies makes the sounds more believable to the audience.

“Caricatures that exaggerate essential facial features have been found to improve recognition,” said Heller, assistant professor of research in psychology, whose interest is auditory perception. “Through the study of auditory caricatures, we are interested in discovering what is essential in a sound for its identification.”

To determine how we perceive sounds, Heller turned her lab into a sound studio to record the real versions of sounds and the artificial Foley counterpart, and to digitally mix the strongest aspects of the two.

More than 70 percent of the time, listeners preferred the hybrids to either the real or Foley version.

Heller will present her findings June 3 at the meeting of the Acoustical Society of America in Pittsburgh.

Although recorded sound effects were available through the Internet, Heller created her own recordings of real events and their Foley counterparts. She opted not to use the available sound effects because there was no way to determine the materials or events that created the sounds.

Heller and Lauren Wolf, a neuroscience student in the Class of 2002, recorded nine events and generated corresponding Foley sound effects.

They included the sound of walking in the mud and its Foley counterpart created by squishing wet newspaper; the sound of walking through the leaves, and the version created by running fingers through a box of corn flakes; the sound of a crackling fire, and the version created by twisting cellophane.

“I did research for Foley effects on Internet sites and there would just be a small description of how to create an effect,” said Wolf, who wrote her senior thesis about the research. “It required a lot of work to get it right.”

Next, Heller digitally synthesized new sounds out of three pairs of sound stimuli: walking through mud, walking in leaves, and crushing eggshells.

She mathematically extracted certain acoustic features – those determined to be the strengths of each – and combined them for the recorded hybrids.

For example, the tempo of walking was extracted from the real recording of a person walking in mud. But the sound of squishing mud was used from the Foley version because it better conveyed the material sound, said Heller.

Research volunteers whose hearing is normal listened through headphones to indicate whether they preferred either of those or the hybrid version.

The Auditory Perception Lab seeks normal-hearing research participants.