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Description
Humans frequently introduce music or ambient sound into everyday environments, often without actively attending to it, suggesting that continuous auditory backgrounds may serve functions beyond pleasure or entertainment. We tested the hypothesis that such backgrounds reduce sensitivity to sudden events, whereas silence leaves the brain and body more vulnerable to acoustic surprise. To probe this, unexpected noise bursts were embedded within periods of silence, music, or environmental sounds while neural and autonomic activity were recorded.Thirty-three participants completed a passive listening task during which EEG and ECG were acquired across 20s epochs of each background condition. Noise bursts elicited heart rate acceleration selectively during silence, indicating greater autonomic reactivity in the absence of ongoing auditory context. Relative to silence, both music and environmental sounds increased EEG ongoing beta and gamma activity, consistent with a more externally engaged neural state. Burst-evoked responses also varied across conditions. Silence was associated with larger early auditory (N1) responses, consistent with increased early sensory reactivity. Music reduced N1 amplitude, suggesting attenuation of the initial sensory impact of surprise in a temporally structured auditory context. Environmental sounds reduced later P2/P3 responses, consistent with diminished higher-order evaluation of the burst. Across conditions, auditory surprisal estimated with the D-REX model predicted P3 amplitude, and higher trait anxiety was associated with larger P3 responses.These findings indicate that silence is not a neutral baseline, but a state of heightened sensory and autonomic responsiveness to unexpected events. Continuous auditory backgrounds, and music in particular, may help regulate this responsiveness by buffering the impact of acoustic surprise.