Harbour porpoises are highly sensitive to underwater noise, with shipping traffic, sonar, and pile driving causing significant welfare harm in coastal waters.
Noise exposure causes acute welfare harm through pain at high intensities and chronic harm through disruption of echolocation-dependent behaviours. Foraging efficiency is reduced in noisy environments, leading to nutritional stress. Displacement from high-quality foraging areas carries energetic costs. Regulatory requirements for noise mitigation during construction activities protect porpoise welfare.