I would use a single reed and only have your mouth partially open,It takes some pratctice.
I will walk around the house and practice or if it drives the wife crazy sit out on the back porch.
You can also hold a piece of cardboard (2'x2') about ten to twelve inches from your face this will give you a idea as to how loud it actually sound's.
Hopefully this helps without confusing you.
I wish you luck.