Pressure Cooking

My mom used to pressure can a lot of things when I was a child, and that canner and the noise it would make would scare me to death.  I have gotten past much of that, and have been using a pressure canner for a few years to can things.  Tonight, I am finally experimenting with pressure cooking food - a beef roast.  At 15 pounds, we are hearing some crazy noises.  Not as bad as the when I was small, but loud.  My kids didn't even bat an eye, and all asked me to lift them up so they could see what was going on with the vent valve and the dial.  I explained what I had put inside of the chamber and asked Eli what was causing the valve to stay up - he almost immediately responded, "Pressure!  The steam is creating pressure."  Smart boy.

I hope this works out - I didn't thaw my roast in time, so I'm hoping this will method will correct for lack of cooking time using my normal methods.