One of the most severe threats to cetaceans worldwide is noise pollution. Ship and boat traffic, military activities, seismic exploration, construction, and drilling are examples of anthropogenic activities that alter noise levels at sea and interfere with cetaceans' sophisticated auditory systems.

Noise pollution can cause marine mammals to leave their habitats, can alter their behavior, impairs their ability to communicate and locate their prey, and masks their acoustic signals over large areas; loud sounds can directly affect their hearing abilities by producing a temporary or permanent hearing loss. All of these effects can be critical to the survival of marine mammals, even to the point of causing injury and death.

The impacts of underwater noise on cetaceans depend on the operational and environmental variables of the sound source and the physiological, sensory, and psychological characteristics of the exposed animals.
Short or single exposures to loud sound can harm single individuals, but continuous noise over time from multiple sources (see maritime traffic) is potentially more serious because it can cause changes in behavior and habitat use that affect entire populations.