Re: [Frameworks] 16mm in the classroom - projector noise!

From: David Tetzlaff (email suppressed)
Date: Tue Oct 26 2010 - 16:03:44 PDT

If you actually attempt to build a projection blimp, I'd suggest looking at some books about building home sound studios, which usually have good info about creating sound isolation.

A big issue is whether the blimp would have to move regularly, or could sit in one place for, say, a semester (and if it has to move, can it be rolled on a cart, or would it have to be lifted and carried). The cheapest and most sound deadening stuff you could make it out of would be particleboard, which is pretty heavy. Also, to kill sound, you want a double wall, a box inside a box, with space between them. Foam doesn't really help that much, at least if it's attached to single walls. If you have a double wall box, it's not necessarily best to fill the space between the walls with foam. Just air might be better. In permanent installations I think they fill the spaces with sand...

If I had (or could build) a suitable rolling cart that could handle the weight, or if the box could sit in place, I'd probably make the walls out of 1/2" or 3/4" particleboard, with a 1/2" to 1" gap between the inner and outer walls. To separate the two walls on the bottom, which would have to bear the weight of the projector, I'd probably use a series of rubber spacers. For the sides i'd try squares of foam glued between the walls, just enough to provide some structural integrity, leaving most of the gap as air (unless some expert source pointed me to a type of foam that definitely improves on air.)

If the whole thing had to be lighter, I'd probably try 3/8" plywood for the outer walls, and the inside layer of the floor. But I might try to make the inner box out of the stiff yellow insulating foam they sell at Home Depot or Lowe's.

In any case, I think both inner and outer layers of the box ought to be tightly sealed with something like silicone caulk (though I doubt that would work with foam inner walls).

For sure, the window for the projection beam needs to be double wall glass, (or maybe inside and outside windows both of insulated glass. The tricky part, I think, would be designing the doors. I think to make it practical you'd need separate doors, a larger one for the outer box, and a slightly smaller one for the inner box (so that it would fully open inside the opening for the larger outer door).

Again, I type this out of memory from guides to studio construction I read over 20 years ago. So I'd definitely do some more research before actually heading of the the store.

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