Sorry but like most things in life it's not quite as simple as a yes or no answer.
Yes an IB can be placed in the attic above a bedroom.
Normal? Define normal.
Could it be heard outside? Yes if it's turned up loud enough. Thing is any type of sub could be heard it was up turned loud enough
To accurately answer questions about the proposed installation I need specific info about the project.
Floor plan Design and placement of manifold or baffle Drivers being used etc etc
Oh Lord! I do good to just get him over here to finish the job. I am positive I won't be able to get him to explain his intentions on here. I wish I could. Better yet, I wish I could have someone like you, who knows there stuff, to come and just finish the job and correctly! Uggghhhhhh! 😕