Re: "Silent" Ukemi
I used to have very quiet breakfalls, and was advised by one (very good) instructor that I should slap to make more noise because that would absorb more of the impact of the fall. I've tried that, and it sort of works, but I found that for me, most of the time, the quiet breakfalls were also more comfortable.
The key factor in developing a quiet break fall, in my experience, is developing strong stomach muscles. Actually, it's probably all of the "core" muscles. Other things that help are practice (duh) and being thrown well. Generally, I have not been able to do silent ukemi from really hard, drill-uke-into-mat throws.