Event-driven changes in near-shore underwater noise during the 37th America's Cup in Barcelona.

Vessel noise is a recognised stressor for marine fauna, yet acoustic pressure from large-scale maritime events in urban coastal settings remains poorly quantified. Using calibrated hydrophone recordings and Automatic Identification System (AIS) data from the DeuteroNoise dataset, we document near-shore noise during the 37th America's Cup (Barcelona, October 2024) against non-event baselines. Broadband levels increased by 5-8 dB re 1 μPa, day-night variability, ∼2.3 dB in the representative summer baseline, collapsed to <1 dB during the event, and 63 and 125 Hz third-octave bands rose by 4 dB during the day and up to 13 dB at night, indicating sustained low-frequency pressure throughout event days.