There was singing in the club wasn't there, which could have masked any noise from the street like doors opening etc. Is a door opening a necessarily noisy event, anyway? Maybe slamming a door up the street might be. I believe it's far more likely to have been noises from the kitchen that startled Jack. There might have been male footsteps on the stair or near the side door, and so he decided to hop it, And perhaps the sound of a horse and cart coming nearer and nearer as well.