When the boys are fleeing their small room by jumping from rooftop to rooftop, Rat says, "Under us and all around us, though, the world was full of noise" (178). To what noises is he referring?

When Rat comments that the world is full of noise as the boys are trying to escape from the police, he mentions the sounds of battering and hammering on doors, engines revving, big dogs barking, and police whistles being blown.