The second hit under the bridge with a dull thud, much louder than the duds heard only on sonar but lacking the whacking noise which accompanies a wholehearted explosion.
Their vocalizations range from soft cheeps to piercing cries, but they lack the screeching voice of other parrots; males are, however, louder than females.
The sound of the instruments changes depending on your location and route through the field of stelae, growing louder or softer, more passionate or muted.