The term listening area, refers to the region of oceanover which sources of sound can be detected by an animal at the center of the space. The lost listening area assessment method has been applied to in-air sounds for a noise effects assessment on birds but not, in our knowledge, previously to the assessment of underwater noise effects on marine mammals. The lost listening area method calculates a fractional reduction in listening area due to the addition of anthropogenic noise to ambient noise. It does not provide absolute areas or volumes of space, as does the communication space method; however, a benefit of the lost listening area method is that it does not rely on source levels of the sounds of interest. Instead, the method depends only on the rate of sound transmission loss. We present a preliminary application of the method from an assessment of “cumulative and chronic effects” of noise produced by oil and gas exploration activities used in the National Marine Fisheries Service's Effects of Oil and Gas Exploration in the Arctic Ocean Final Programmatic Environmental Impact Statement.