Bro, this was the first PS1-style game I've played; you did an amazing job for a debut title. The only issue was that you hadn't set up the mesh colliders.

Your problem is sound. Look at the red bar at the bottom of the screen – that's your noise meter. If it gets full, you're dead. Walk slowly (use the sneak key) and while opening the door, watch the bar carefully so it doesn't max out

(: