What to do about my boss/roommate yelling at her kids all day everyday?

I work as a nanny to 3 kids, and one is very difficult with huge emotional and behavioral issues. I have received numerous compliments from friends and there family on the positive changes that have came about since i have been there nanny. They went through 6 nannies in 3 years, and i am the only one who has stayed and taken an invested roll in the girl, of which i have been told no one else could get along with her. Well my question is, part of my pay, which is i believe to be below minimum wage, is to live at the house, since the mother works 24 hours shifts. I do not make enough to pay to live anywhere else. Well the problem is that the mother yells at the kids all the time, almost 6 to 10 times a day, i hear her yelling, and it seems to always be right outside my bedroom door, or my window, at ground level. I "hide" in my room constantly when the mother is here, part to give them there space, and privacy, and part because i do not enjoy interaction with the mother, because she always asks me to work overtime without pay, and she is always in a bad mood. the yelling is so distracting, and starts as soon as the kids get home from school, or when the whole family gets home from going somewhere. I can barely get anything done, from work, paying bills, all the work people have to keep up on, (looking for a new job), my entire to do list. The family is on vacation this week and i have been so productive with getting stuff done, that i have realized just how bad her yelling is effecting my emotional well being, and productivity. I have tried working in my car, and to hot this time of year, and i go to the library which is the best alternative, but then need to go get food, etc, and end up spending money, and not getting alot done because of people talking, or loud kids at the library. i would appreciate some idea's as to what other people would do in this situation. I am looking for another job, but with this economy it is a bit of a slow process. I feel if my room and board are part of the pay, i should have a right to a peaceful environment, and not have to listen to all that yelling, of which it doesn't take to get the kids to behave, they do just fine, and i NEVER yell at them, so as to show them that isn't the only way to communicate. Also when there mother is here, all the kids yell alot also, and the girl screems all the time, and fights with her brothers, when im on duty and the mother is gone, non of the kids yell, or scream or fight. It is very peaceful when she isnt here, and when she is, you can tell the anxiety of the kids goes through the ceiling, as does mine. If i were to say something to her, what would be appropriate? Thank you so much for taking the time to read this and respond. I really just would like to know what other people would do, or how it would effect them. thanks!! please no rude or snot-tie responses, my stress levels are off the charts from all the yelling, and the world needs more kind people, not people who can not control themselves :)