When you're struggling to make out the sound of someone's voice in a crowded restaurant, do you ever shut your eyes to hear them better? New research says you're probably not doing yourself any favors.
A study published in the Journal of the Acoustical Society of America debunks the misconception that removing visual distractions will help you pick out sounds you're straining to hear. The research team asked participants to listen to sounds through headphones while low noise played in the background. While they listened, they were assigned to one of four different visual conditions: Eyes closed; Looking at a blank screen; Looking at a photograph related to the sound; Looking at a video that matched the sound.
Participants found the task hardest when their eyes were closed. With their eyes open, even if they were looking only at a blank screen, they could discern sounds an average of 1.32dB quieter than they could with their eyes shut. Relevant visual information improved their performance even more. Viewing a related photo helped them pick out the sound at volumes 2.92 dB lower. A sound-matched video? 4.30 dB lower.
"Contrary to popular belief, closing one's eyes actually impairs the ability to detect these sounds," explains study author Yu Huang. "Conversely, seeing a dynamic video corresponding to the sound significantly improves hearing sensitivity."
Data on participants' brain activity during the tests offered a hint as to why this might be the case. Electroencephalography (EEG) showed that closing their eyes shifted participants' brains into a state where incoming information is filtered more thoroughly. This increased filtering likely muffles sounds we're trying to hear, too. "In a noisy soundscape, the brain needs to actively separate the signal from the background," says Huang. Visual information can assist by showing where a sound is coming from or what may be making it.
If you're having a conversation at a restaurant, the way their mouths move as they speak can give you critical context. When a person can see your mouth, they have extra information to fill in the gaps.
The new study's findings apply to noisy environments, but a paper from the University of Lübeck showed that, even in a quiet room, closing your eyes doesn't necessarily improve your hearing performance. Closing eyes increased alpha oscillations in their brains, a marker of auditory attention. They didn't actually perform any better at picking out the sounds, though, than when they had their eyes open.
In other words, closing your eyes might help you focus, but it doesn't improve your hearing.