Over the past few years the increase in human population worldwide has changed the underwater soundscape. Loud, new, unfamiliar noises are being introduced to the environment, impacting many species of animals. This has particularly harmful effects on marine organisms that rely heavily on their sense of hearing, such as harbour porpoises (Phocoena phocoena). Harbour porpoises use echolocation to navigate, to orient themselves in the water column, to communicate with one another, and to detect prey. The introduction of impulsive noises into their habitats can be detrimental to this sensitive species, as it may cause them to undergo adverse behavioural reactions, stress, physical injury and sometimes death. The aim of this study is to assess how impulsive pile-driving noise has an impact on the harbour porpoise distribution in the Belgian part of the North Sea (BPNS) through passive acoustic monitoring.