Here's my DIY method of making a SUPER simple sound isolation booth for recording vocals (that really works!) without impressive tools or expensive materials.
Easy. Foolproof. Inexpensive. Functional.
Cardboard Box (or another material box) (mine was about 2 ft x 2 ft, with a depth of about 5 inches)
Mattress padding foam
Black spray paint (optional)
Adhesive (simple or hot glue and some double sided tape works great!)
1) Start by planning the shape and dimensions of your box. I decided to make mine a trapezoidal prism by folding in the top and sides of the box. I can also unfold it into a shallow box with two side foldings. You can also make a rectangular box, or another shape.
2) Mark your box in such a way that you know where your boundaries are if you are folding the box in like I did. Also be sure to plan where you'd like to place your microphone. Mark and cut out a mic hole.
3) Spray paint the outside of your box if you desire.
4) After your box dries, measure the dynamics of each flat portion on the inside of the box.
5) Cut your mattress foam into pieces to fit the insides of the box. Mark the back foam piece where it lines up with the microphone hole in the box. Cut a simple X into the foam, so that the microphone can be slid into place, but the foam can be snug around the microphone.*
6) With the textured side of the foam facing up, attach the foam to the inside of the box.
7) Using the extra foam slivers, squish little pieces into the corners and edges of the box. If necessary, use duct tape to help the box keep its shape.
8) Slide your microphone into place and press record!
* If your microphone sits on a simple stand, you can cut a hole in the foam the size of the base of the stand, and place the mic towards the back of the box standing in the hole in the foam.
I hope this method works well for you! Comment tips, thoughts, or other ideas for DIY at home recording. I hope we all make it big and someday have real sound booths...but you've got to start somewhere!