Habitat loss is a leading cause of biodiversity loss in terrestrial ecosystems. For marine species that rely on acoustic cues to navigate, find food or select mates, sound is a key element of their environment. Chronic forms of human-generated ocean noise have the potential to mask communication signals over substantial fractions of their functional areas for substantial fractions of the year, which makes acoustic masking a qualitatively similar stressor to habitat loss. International policy decisions on chronic ocean noise are evolving, which creates an opportunity to advance the scientific foundation of decision-making. We measured ocean noise levels at 12 sites, chosen for current and predicted intensities of anthropogenic activities and importance to three endangered whale species in Canada's Pacific Ocean: fin, humpback and killer whales. Canada includes sound as a key element of resident killer whale critical habitat, but not for other species. In the frequency bands that killer whales use for social communication, noise levels were highest in legally designated killer whale critical habitats. In contrast, noise levels were generally lower in habitats known to be important for baleen whales, but these quieter areas are not yet given special legal protection. These noise levels translate into potentially serious fractions of lost opportunities for acoustic communication. Median noise levels are high enough to reduce the communication spaces for fin, humpback and killer whales under typical (median) conditions by 1, 52 and 62%, respectively, and 30, 94 and 97% under noisy conditions. As countries begin to articulate their policies to protect acoustic attributes of marine habitats under their jurisdiction, we recommend quantifying loss of communication space, but quantitative targets need to be set. We see two ways forward. Managers could specify limits of acceptable change in terms of population-level impacts, which can be modelled through effects from communication masking and/or disturbance on prey intake. Alternatively, managers can specify targets reflecting amount of habitat to protect for each species, adjusting upward to account for habitat effectively lost from chronic ocean noise.