One possibility is AD(H)D, which can cause heightened sensitivity to noise, touch, etc. I've got ADD and sometimes noise can be a powerful distractor when I'm trying to focus on something intensely.
However, I'd guess that your mother's hypersensitivity has become, as you say, a handy "excuse" for laying the blame elsewhere when she wants to indulge herself -- she hasn't learned the proper adult coping mechanisms for dealing with life and its stress. Sounds like she'd REALLY benefit from some therapy, but chances are you will have no control over that ...
If this is at all applicable, check out a fabulous support group for adult children of parents with personality disorders:
http://groups.yahoo.com/group/ModOasis
You might find a lot of unexpected support there for your mother's raging and other issues --
Best of luck!
Helen
Thanks so much for the info & advice!!!
I also have an intolerence to certain sounds. Not as extreme as I am hearing about in your case, but sometimes it sends me into a corner or closet, crying and covering my ears. It happens more during my depressive episodes. I realize that it is not a problem with my ears, entirely. Like a said, sometimes the sounds intensity seems worse than at other times. My suggestion...Try ear plugs, they make soft, malable, foam ear plugs that can be very descreet. It will muffle any sound and she will tell on herself when she has to tell someone to speak -up. Good luck!
Jai
I do not know of a specific disorder that would cause these, but it is certainly possible that she is one with greater than normal aural acuity just as a matter of genetic differences. She could get her hearing checked to see if that is true. On the other hand, she may just be anxious, which can also cause irritability and a stressed out response. In that case, some antianxiety drugs, like klonopin, would be useful.
P.S. She's been to a doctor about her hearing & he said there was nothing wrong. That's why I was wondering if it may be something psychological? Someone once told her they heard about a syndrome that causes hyper-sesitivity but didn't know what it was. She latched right onto that without checking into it & uses it as an excuse for her flying into a tantrum.