Before you can look at some accepted ways to improve your isolation, it’s important to look at all the things that won’t work first. This excerpt from The Studio Builder’s Handbook (written with Dennis Moody) contains a list of various materials that you’ll often see attached to the walls of a space in hopes of increasing the isolation. The problem is that they won’t help very much at all.
Mattresses – There are so many things wrong with this that it’s hard to know where to start. Sure mattresses are made up of a lot of soft material, but it’s not the right kind for sound absorption, won’t affect the low frequencies at all (which are what causes most of the the isolation problems), accumulates mold and moisture, and makes nice homes for rodents and other unwanted critters. Plus, it’s pretty difficult to get enough of them to cover a room, and they take up so much space for so little benefit in return.
Egg Crates – Egg crates are light porous cardboard and do absolutely nothing for soundproofing. They can act as a sound diffusor at higher frequencies, but the bandwidth is so limited that they’re virtually useless there as well. Plus, they’re highly flammable! It’s difficult to find enough of them to cover a room, but frankly, even using one is too many.
Carpet – Carpet attached to the wall is another product that will affect the sound of the room yet do nothing in the way of soundproofing since it doesn’t affect the low frequencies, which are the ones that you’ve got to control for good isolation. Carpet has exactly the same problem as mattresses in that it will begin to smell over time. Old or new carpet makes no difference, except that older carpet will smell more.
Foam Rubber – Foam rubber does have some acoustical absorption properties, but once again will do very little for the low frequencies that will cause all of your problems with the neighbors. It’s can be as expensive as materials with real acoustic control properties, degrades over time, and will burn like crazy if given the chance.
Rubber - Floor matts, mouse pads, neoprene, or any other variation of rubber will do very little to stop sound coming or going from your room. Once again, it’s much cheaper to buy proper acoustic materials that are easier to work with, but they won’t help your isolation problem either.
Wall Cellulose – Pumping cellulose insulation into walls can make a slight difference, but it’s marginal since there are much more effective ways to improve the isolation that are much cheaper. It can be helpful if used along with some other techniques that we’ll soon go over, but isn’t particularly effective by itself.
Fiberglass Insulation – Common fiberglass insulation once again has little ability to stop enough of the low frequencies that bug your neighbors, although, like with blown cellulose, it can be useful in conjunction with other techniques. Just pinning it to the wall won’t help though, but it will affect the acoustics of the room. It’s also a skin and eye irritant, takes up a lot of space, and the dust can be hazardous to your lungs when left exposed. As you’ll soon see, there’s a much better way to use fiberglass for acoustic control (although it still won’t help with isolation much).
Plywood Panels – It’s true that plywood panels provide mass and mass is what’s needed to stop sound transmission (especially the low frequencies), but the problem is that wood transfers sound too well so the construction technique used is crucial. Not only that, if the panels are too thin they’ll resonate and vibrate, causing an even bigger problem.
Particle Board – See plywood panels.
Bales Of Hay – Unless you live out in the country, it’s unlikely that hay bales are much of an option, but they actually do work. The problem is that they take up a lot of usable space, make a nice home for critters, and are a major fire hazard. Not recommended
Acoustic Foam – Acoustic foam is helpful in controlling the acoustics within a room, but it does nothing to stop sound transmission and is expensive to boot. Acoustic foam doesn’t even begin to affect the offending low frequencies, and using too much just makes the room seem dead and uncomfortable. There are much cheaper ways to achieve a better result.
Understand that all of these materials will have at least some affect on the sound of the room (which is covered in another chapter of the book), but will do almost nothing by themselves to help improve your isolation.