Record the dimensions of your studio using a measuring tape. Best soundproofing results are achieved when all of the walls are covered with foam, so precise measurements are important.
Purchase enough acoustic foam to adequately pad your studio. Foam can be purchased in panels, typically 24 inches long by 18 inches wide at roughly $9 each from most retailers, or in bulk rolls. Acoustic foam with a thickness of at least two to three inches will offer the best noise reduction.
Mount the foam on your studio walls using a staple gun. If you've purchased a bulk roll of foam, use a utility knife to cut the foam to appropriate size.
Cover any gaps that noise can travel through (cracks under doors, window panes) with egg cartons. Dense piles of dirty laundry can also be used to cover large areas of noise leakage.
Fill any small seams with a thick bead of polyurethane caulk. Cracks in windowsills, door frames and other seamed areas allow noise to escape from your studio.