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Researchers from Shanghai Jiao Tong University published a study in JASA that challenges the common assumption that closing your eyes helps you hear better in noisy situations. Using EEG monitoring, the team found that in noisy environments, eye closure puts the brain into a state of "neural criticality," which causes it to over-filter incoming signals, suppressing both background noise and the target sounds a person is trying to detect.
In the study, 25 participants listened for faint target sounds through headphones over constant background noise of 70 decibels, roughly equivalent to a busy city street. They performed the task under four visual conditions: eyes closed, eyes open facing a blank screen, eyes open viewing a still image corresponding to the sound, and eyes open watching a matching video. Eye closure produced the worst detection performance of all four conditions. Watching a matching video produced the best. The average detection threshold worsened by 1.32 decibels with eyes closed, while the matching video condition improved it by 2.98 decibels.
The authors note that the finding is specific to noisy environments. In quieter conditions, eye closure may still help. The researchers plan follow-up work to determine whether the benefit of visual input comes from simply having the eyes open or from seeing content that matches the target sound. The study has potential implications for hearing aid design, auditory rehabilitation, and training in environments where detecting sounds in noise is critical.
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