A study published in JASA, on behalf of the Acoustical Society of America by AIP Publishing, set out to test whether closing the eyes truly improves hearing under noisy conditions. Researchers from Shanghai Jiao Tong University examined how visual input affects the ability to detect sounds.

Experiment Testing Hearing in Noise

Participants in the study listened to a range of sounds through headphones while background noise played at the same time. Their task was to adjust the volume until each sound was just barely audible over the noise.

The experiment included several visual conditions. First, participants completed the task with their eyes closed. They then repeated it with their eyes open while looking at a blank screen, followed by viewing a still image related to the sound, and finally watching a video that matched what they were hearing.

Closing Eyes vs Visual Cues

The results went against a widely held assumption. "We found that, contrary to popular belief, closing one's eyes actually impairs the ability to detect these sounds," said author Yu Huang. "Conversely, seeing a dynamic video corresponding to the sound significantly improves hearing sensitivity."

Rather than helping, closing the eyes made it harder to pick out faint sounds in noisy settings, while relevant visual input provided a clear advantage.

Brain Activity and Over-Filtering

To understand why this happens, the researchers used electroencephalography (EEG) to track brain activity during the tests. They found that closing the eyes shifts the brain into a state known as neural criticality, which increases how strongly it filters incoming information.

This heightened filtering does not just reduce background noise. It can also suppress the target sounds participants are trying to hear.

"In a noisy soundscape, the brain needs to actively separate the signal from the background," said Huang. "We found that the internal focus promoted by eye closure actually works against you in this context, leading to over-filtering, whereas visual engagement helps anchor the auditory system to the external world."

When Closing Your Eyes Still Helps

The researchers noted that the effect appears specific to noisy environments. In quieter conditions, closing the eyes may still improve the ability to detect subtle sounds.

However, since everyday life often involves significant background noise, keeping your eyes open may be the more effective strategy in many situations.

Future Research on Vision and Hearing

The team plans to continue studying how sight and sound interact. One key question is whether the benefit comes simply from having visual input or from seeing something that matches the sound.

"Specifically, we want to test incongruent pairings -- for example, what happens if you hear a drum but see a bird?" said Huang. "Does the visual boost come from simply having the eyes open and processing more visual information, or does the brain require the visual and audio information to match perfectly? Understanding this distinction will help us separate the general effects of attention from the specific benefits of multisensory integration."