Jack was just about to remind the Doctor he 'lost' him for quite a considerable amount of time, actually. But instead he was distracted by the noise, and he immediately stepped to his feet and moved to the door.

He pulled his sonic from his pocket and tried it on the door but it was deadlocked, no surprise there.

"Look, whoever you are and whatever your deal is with the Doctor, you've picked a bad time. This is gonna have to wait. And you better open this damn door!"