Sound of silence (Image: Viktor Drachev/AFP/Getty Images)

IS A sound only a sound if someone hears it? Apparently not. Silent videos that merely imply sound – such as of someone playing a musical instrument – still get processed by auditory regions of the brain.

Kaspar Meyer at the University of Southern California in Los Angeles and colleagues showed eight volunteers nine silent video clips that implied sound, including people playing violins, a dog howling and chainsaws cutting into trees. As they watched, their brains were scanned using functional MRI.

Each type of implied sound created a unique pattern of brain activity in …