Monitoring marine ambient sound using standardized methods supports assessments of ocean sound levels across widespread ecosystems. This thesis quantifies differences among coastal and deep-water marine soundscapes in the Atlantic and Pacific oceans. The sources of sound in a soundscape are compartmentalized into three components and compared over time and among different areas to give insight into the status of ocean ecosystems, revealing the presence of vocalizing animals, anthropogenic activity, and environmental changes such as weather (e.g., wind, rain) and ice coverage. Assessment of acoustic differences across discrete soundscapes supports the work of policy and planning leaders to address issues dealing with monitoring protected areas and marine species (marine mammals, fish), and the contribution of anthropogenic sources to ambient sound associated with energy production (oil exploration, renewable energy development) and socioeconomic activity (container shipping, commercial fisheries, and sport watercraft). These data also define a baseline to evaluate changes over time, including the presence of anthropogenic activities, and the efficacy of management approaches addressing both protected areas and species.