Purchase some Owens Corning 703 acoustic rigid fiberglass. This is the most common and most effective material used in sound absorption and acoustic projects. Typically, you can purchase it in sheets that measure 24 inches by 48 inches by 2 inches. Each panel will consist of one sheet, so purchase one for each panel you plan to build. Purchase two eight-foot lengths of 1 by 4 boards. You will need a miter saw or radial saw to cut the boards to the proper lengths. You will also need a drill with both a pilot bit and a screwdriver bit. You will need at least twelve wood screws, preferably 2 1/2 inch lengths. A measuring tape and a heavy-duty stapler will come in handy as well. Finally, you will need enough fabric to cover the panel. The type of cloth to be used can vary, but if air can easily pass through the weave, it should be fine. The fabric should not be so tight a weave that air and sound is reflected from it rather than passing through to the absorbent fiberglass.
Lay the fiberglass sheet flat on the floor of your workspace. Cut one of the eight foot 1 by 4 boards perfectly in half. Each of these pieces will serve as framing for the long sides of the fiberglass. Using the remaining 1 by 4, cut two boards that measure 2 1/2 inches each. Essentially, you will now build a box frame for the fiberglass. Assemble the boards around the fiberglass in the frame position. Using the pilot bit, drill pilot holes for the wood screws. Wood that is as thin as one inch can easily split, ruining the project. If you drill a pilot hole first, the screw drops more easily into the wood. Each joint should have three evenly spaced pilot holes for screws. Drill the holes from the shorter boards into the longer boards. The measurements given will provide a very snug fit for the fiberglass in the frame. It may seem like the fiberglass is only slightly too big for the frame. This is desirable, however, in order to hold the fiberglass in place without actually drilling into it.
Measure the fabric to cover the front of the panel completely and wrap it around to the back framework. Pull the fabric tight. Using a heavy-duty stapler, staple the fabric to the framework. To hang the panels, it is appropriate to hang them as you would a large picture or painting. Use picture hanging wire, or attach hanger hardware to the back and place them where desired in your rehearsal space or home theater.