The focus of this thesis is the use of sound for communication by the North Atlantic right whale (Eubalaena glacialis). The surface active group (SAG) is the predominant social interaction in this species for which use of sound has been documented. Different group compositions in SAGs indicate that both potentially reproductive and non-reproductive groups have been combined under one label. Sound production in SAGs suggests that females form and maintain the groups by producing Scream calls. Males produce Upcalls to advertise their presence as they come into a group or when the female is on a dive. Males may use Gunshot sounds as threat signals to other males in the group or potentially as reproductive advertisement signals to the female. Some calves produce Warble sounds in SAGs. This may be limited to female calves. This description of acoustic activity in the groups adds to the picture of the SAGs as complex interactions between individuals, rather than simple groups with only one whale producing all the sounds to attract other whales to the group. Playback experiments demonstrate that right whales can use sounds from SAGs to locate the groups. Male right whales approached both North Atlantic and Southern right whale SAG playbacks. Female right whales only approached Southern right whale playbacks. Anatomical modeling resulted in a frequency range of hearing for the right whale (10 Hz - 22 kHz) that is consistent with the sounds that they produce and overlaps the frequency range of most anthropogenic noise sources. This combination of research provides a thorough description how North Atlantic right whales use sound in SAGs and how increasing levels of noise in the oceans may impact right whales in these groups.