Harbor porpoises are among the most noise-sensitive marine mammals, and underwater noise pollution from shipping, sonar, and offshore construction causes significant welfare and population-level harm.
Harbor porpoise noise welfare encompasses both acute and chronic harm. Acute harm from pile driving includes physical tissue damage from pressure waves if animals are too close, causing temporary or permanent hearing damage that compromises their echolocation ability - essential for hunting and navigation. Chronic harm from continuous shipping noise forces animals to increase their own vocalisation effort to communicate, causing acoustic fatigue. Noise-stressed porpoises in affected areas show altered movement patterns and feeding behaviour. Mitigation measures including soft start procedures for pile driving, acoustic monitoring with automatic shutdown when animals approach, and bubble curtains reduce acute harm. Shipping speed reduction reduces chronic noise exposure.