A common science project assigned to middle school and high school students is to make a soundproof cardboard box. A soundproof cardboard box also can come in handy when recording music---a guitar amplifier can be placed inside the box with a microphone to isolate the sound. The following technique can be used to soundproof any type of box or enclosed area.
Measure and cut the styrofoam sheets into squares or rectangles that will fit inside the cardboard box. You will need to cut a total of ten sheets, two for each wall of the box (the four sides and the bottom).
Cut five pieces of sound deadening that match the styrofoam rectangles, one for each wall of the box. Sound deadening is a material made to soften sound; it is often used in cars.
Glue one sheet of styrofoam to each of the four sides and the bottom of the inside of the cardboard box.
Glue the five pieces of sound deadening over the first layer of styrofoam.
Glue a second layer of styrofoam over the sound deadening.
Add more layers of styrofoam and sound deadening to further muffle the sound.