 SYNC: In the scene following the defeat of the troll, Quirrel is  shown speaking with the other professors, at which point they, and  the trio, leave the girls bathroom. Their footsteps are clearly  heard as they move down the hall; however, in the next shot of the  troll laying on the floor, the sound effects have ceased. In the  last shot, of Quirrell jumping nervously in response to the troll  grunting, the footsteps can again be heard.