Sonic damage is dealt by violent molecular reverberations/vibrations caused by sound energy. Despite being energy-based, rather than element-based, the resist elements line of spells do protect against sonic damage.
This damage type is one of the rarest in NWN — but not as inaccessible as positive energy damage — making it a popular surprise choice for player characters in PvP environments. Some examples of spells causing sonic damage are sound burst and wounding whispers. Sonic damage can be reduced via the feats resist energy and epic energy resistance, and sonic immunity can be obtained via the spell silence.