I'm working with a friend to work on his Music room. It is in the basement, so that's the good part, however, he has 2 big windows (2' x 4') in it that the sound travels through pretty well. What kinds of things can we put over the windows (don't need the light) to block the sound. This is a rental property, so we can't do too much to the windows.

I checked some foam squares for Noise Absorbtion, but that is just for preveting reverb and echos of sound, not preventing sound from going through it. Maybe a few layers of dense cloth of some sort will work?

I read a few resources online and they all say that dense, heavy things work the best for blocking the sound. Any ideas?

Eggshell foam would be a good choice.

When I've wanted to isolate my amp, I've used a combination of mattresses and any clothes I could find lying around my room.

I'd get a couple of mattresses up by the windows. They work well and are no t permanent.
If the windows are small, attach pillows to them

Windows 3.1

I got some good ideas form a message board that is all aboud home recording studios. We are gonna try it without the soundproofing first, to see if it works.

If you're looking for a heavy fabric, you might look into getting some canvas tarps, but a heavy grade canvas tarp will be very expensive.

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Are you trying to sound proof for the sake of keeping out the outside noise, or for the sake of keeping your neighbors from hearing the noise.

I think, if you bring in too much foam and cloth, it can actually begin to affect the sound in a bad way.

At the recording studio where I've recorded in the past, the sound was isolated by the "thickness" of the walls, the glass, and the doors.

For example, I recall that the doors were three layers thick, and that they were constructed of a really solid, high-density wood. Knocking on the door was almost like knocking on a brick.

Since the door was equipped with a conventional door knob, in order to add the two additional layers of door, they had to cut out the area around the door knob, allowing just enough room to put your hand in there and turn the knob. I have no clue how they actually put the doors together like that, but I imagine that it could be accomplished with a drill, some wooden dowel rod, and some decent wood glue.

From memory, I do not recall there being very much foam in the room, but there may have been some installed in the upper corner of each wall, along the edge of the ceiling.

In this application, I don't think that the foam was meant to sound-proof the room, but simply to reduce the echo, so that the room would have a nice, warm sound.

The floors in the studio were wooden.

However, in a situation where the studio floors are carpeted (in a home studio, for instance), there is probably no need to add foam, because (in theory) the carpet should absorb most of the echo.

Joe

carpet pad works great.

I would use a nice piece of some acoustic type foam, then put a board or something over it, and then put a layer of the acoustic foam over the top. (if you cant afford, or dont want to invest in the spendy acoustic foam, find a nice foam that has good sized air holes in it, everytime sound hits a pocket of air it helps deaden it...
anyway, thats what I think...
i play really loud, and have played in some basements with windows, and thats how we kept the cops from showing up...