As soon as I read that he attacked whenever there was a loud noise or boisterous person, it made me think that it may be some type of seizure. I had seizures as a child and I can tell you that things like fireworks and bright lights would bring one on. Perhaps your kitty has a brain disorder, as has been suggested. If not, Emeraldgreen mentioned that I've had great success w/a med called Clomicalm. It was originally prescribed for behavioral problems in dogs but has been used successfully w/cats. I have 4 of them on it presently, all 4 for inappropriate urination and one of them also for aggressive behavior (attacking my other cats). It's been a godsend to me. Some vets say that it takes a while to start working but I saw immediate success w/it. If you have your cat checked out and a brain tumor or disorder is ruled out, you might want to give Clomicalm a try. It isn't that expensive for one cat and it may be the answer you're looking for if the problem is not indeed medical. Good luck. I know it's tough and you do have your future baby to consider but I think w/a little investigating, you can come to a solution.