Hey, I subscribe to the magazine, but didn't know until today that there is a forum here. Nice.
So I need to make a sound proof box, and hopefully on the cheap, because I'd like to make a few of them. The interior of the box doesn't need to be any bigger than say (2"x4"x2") The exterior size isn't limited so much, maybe a foot cube, but just so long as it fits reasonably on a desk and can be carried. But I need to be able to get into the box fairly easily.
I'm mostly curious how people would soundproof it. I figure I'll start with some sort of metal box for a structure and layer around the outside. But I'm not sure what the best materials would be to do that.
Well, it would probably peak at 90-100 dB. I'm using it as a control, so its probably closer to say that I'm trying to keep sound out rather than keep it from getting out.
I built a human-sizes sound proof booth once for hearing tests. From the outside in, it was constructed with;
3/4" marine plywood 2" foam rubber (uhpolstery store) 2" of unpapered fiberglass insulation compressed to 1" 1 layer of 500 TPI broadloom cloth (to contain any fiberglass particulates) 1 layer coated pegboard ( to make the inside cleanable) silent, and anti-echoic. It worked very well. John
Frodus and jschuch, thanks for your input. Frodus, When I see a figure like this for dynamat ( 0.29 @ +20C (+68F))
Do you know if that means that if 1 is normal sound, then using one layer of dynamat, the resulting sound would be .79. Two layers would be yield .62 or (1-.29) ^2
jschuch: do you know how much you were able to reduce the dB's? Did you have any way to quantify how much the sound was reduced? Also, which do you think reduced the sound more, the foam rubber or the fiberglass insulation?
WAY back then I didn't have access to any decent test equipment. My -subjective- test... I sat in it with about 45 screaming 8-year old outside it and I could not hear anything but the rush of blood through my ears (strange sensation).
I believe the foam was more absorbtive, and the fiberglass more anti-reflective.