Mojofunkster, I heard the exact same thing. I noticed it in the scene when the boys enter the sewer by the river, after Ben gets cut and they find the missing girl's shoe. I can't imagine that was an artistic choice. I'm guessing they cleaned it up in post and decided it wasn't worth ADR, or schedules wouldn't allow for it- who knows. It was obvious on the super loud IMAX theatre but if i had been watching at home i may not have noticed.