Materials for soundproofing?
Question:Say I wanted to soundproof a small container (about 1 cubic foot) so sound cannot escape the container. How would I go about doing this?
Is it possible to soundproof (or at least soften the sound) it with material that still allows me to see into the box?
It is okay if the material just softens the sound and doesn't eliminate it.
Answers:
You don't say what level of soundprrofing you consider adequate or the source of the noise in the box, so it is very difficult to be precise.
That said here are some general suggestions. Soundproofing can be considered as a combination of damping and blocking the transmission of sounds. Generally it is fairly easy to block higher frequencies and difficult to block lows.
High frequencies will be blocked if the box is sealed. How you accomplish this is up to you but basically requires the container to be essentially airtight (although it is possible to not have it airtight if some type of baffle (e.g. a muffler) is used) so non porous, heavy weight panelling should be used. Non (or at least low) resonant material like medium density fiberboard (MDF) is preferable to plywood.
Mid and low frequencies require damping of the sound probably best accomplished by building one box inside a larger box and isolating the inner from the outer with some type of elastomeric material (e.g. rubber, non hardening caulking). Filling the space between the boxes with fiberglass insulation will reduce resonance transmission. The greater the mass of the box the better (This is why concrete blocks or multiple layers of shock mounted drywall are effective in soundproofing rooms).
Your requirement to be able see inside the box can be accommodated by using two double (or triple) layer sealed glass units (sometimes called Thermopane) inset into one side of the inner and outer box with a rubber seal or elastomeric caulking around each (remember the need to seal the box for high frequency isolation).
Recognize that sound reduction by 30-40 decibels across the audible frequency range should be attainable fairly readily, and with greater care possibly 50-55 db.
Well, it depends what you are keeping in the container. Because you can use egg cartons.
With all due respect, and I see this answer so often, egg crates make a poor sound deadening material. ( I HAVE NO DOUBT I"LL GET THUMBS ON THAT)
I do agree with answer one though in your purpose which you don't state.
In a box that size depending on the purpose I'd get a small piece of acoustical cone foam material, like studios use... OR that is often used in cases designed to carry delicate objects.
SEEING into the box can be accomplished with glass or plexi which have little sound deadening qualities.
Steven Wolf
Sheetblock. http://www.auralex.com/sound_isolation_s...
Thin vinyl like material that a transmission barrier. Unfortunately comes in fairly large rolls since it's a construction material.
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