...you should be able to do what you want in your 16 by 20-inch room.
What's in there now, and what is your budget?
First, get a few cans of acoustical foam and seal EVERY penetration in the floor, walls and ceiling.
Best bet is to build a wall within a wall...but I'm guessing that's a budget-buster.
Resilient channels and two layers of drywall w seams offset? How about Homasote board?
The channels and one layer of drywall/Homasote?
Thick padding (use in quilt making, etc) covered with fabric on the walls/ceiling?
Rubber mats on the floor?
Ever see those "dressing screens"...about 6'tall, made up of three or four hinged panels? Get a few of those w foam/fabric covered panels, and set them up on opposite sides of the room with the panels "zig-zagged." The idea is to keep sound waves from reflecting off opposite parallel surfaces in the room.