In the recent listing of southern resident orcas as endangered under the Endangered Species Act, disturbance by vessels is cited as a risk factor for the population and a factor in the designation of critical habitat. To help determine whether vessel noise underwater is disturbing orcas as they use sound to navigate, forage, or communicate, the source level of common large vessels transiting Haro Strait was measured. Since large vessels are the dominant source of underwater sound for the southern residents (based on water volume ensonified and duration of exposure at a given receive level), it is convenient that all commercial vessels longer than 65 ft are now required to broadcast their location, speed, and other data in real-time. The automatic identification system (AIS) broadcasts data every 2 s via VHF that can be received and decoded with specialized radio receivers that are now coming on the market. AIS was used to log range, speed, and relative bearing while simultaneous recordings were made of the received sound pressure levels using calibrated hydrophones and photographs were taken. From these observations, the broadband and spectrum source level of each vessel was calculated as a function of bearing relative to vessel axis.