We've had our cat since she was a kitten, about a year and a half now. She is normally a pretty good cat and only shows aggression when I've attempted to bathe or groom her, or when our 4yr old gets too rough with her. I have 2 other kids from a previous relationship who rarely visit. However, whenever they do visit us the cat goes bezerk. I'm not certain if she can smell their cats on them and this is a territorial issue or not. After her last freak out I put the cat in the basement to cool off. As I went to go downstairs myself a while later she greeted me at the top of the stairs and seemed to be calm and docile again. I was holding and petting her but all it took was my son's voice heard through the door and she began to hiss again. Is it possible there is something about his voice that irritates my cat?