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Recently I started looking at the acoustics of my home
studio and spent a some time doing research on how to isolate and improve the sound of my
room. I thought that the next two months I would share some of the knowledge I gained. While I avoided any major structural modifications, bear in mind that it is
sometimes necessary to do some construction to gain the effect you are looking for. |
What is Soundproofing?
The first thing you need to understand is the difference between
soundproofing and acoustic treatment, as the two are often confused. Soundproofing cuts
down noise that is transmitted in or out of your studio. In other words, stopping your music
from disturbing the neighbours, as well as keeping the sound of passing traffic or barking
dogs from becoming a part of your latest masterpiece. Acoustic treatment (which I will
cover in part two of this article) controls the quality of sound in a room, making it more
neutral. If your room has less effect on what you hear, you are more likely to create
mixes which are "portable", i.e. that will sound good on different systems in
different listening environments. Whatever you may have been told, you cannot soundproof with egg boxes, acoustic
tiles, foam or carpet. These are used for acoustic treatment not soundproofing.
The Mechanics of Soundproofing
Without building your studio from scratch, using special
construction techniques and materials (which are beyond the scope of this article and the
budget of most of us), it is impossible to reach perfect soundproofing.
The simplest way to attenuate sound is to put a solid, dense
barrier in its way - the more solid and dense, the better the isolation. A second barrier
spaced apart from the first will improve things even further. In fact, this will always
give better results than a single barrier of double the thickness. The wider the gap, the
better the isolation, especially at low frequencies. Unfortunately, the efficiency of
isolation falls with frequency - this means that while you should be able to isolate the
mid and high frequencies totally, chances are you'll still be able to hear loud bass
instruments from outside and some traffic rumble from inside.
It is critical that an acoustically isolated room is
airtight (or as close as possible). A small hole in any barrier, such as a hole cut for
wiring or an electrical outlet, can reduce the effectiveness drastically. A one-inch
square hole cut into a 100 square foot barrier reduces its sound blocking capability by
70%.
Walls
Luckily, here in South Africa, the vast majority of buildings are
constructed with masonry which has very good sound-isolation properties. It is
generally other areas of the room which are problematic.Outer walls are often double which
further improve matters (although not as much as if there were a space between them).
Windows
Windows, ideally, should not exist at all! But if you cannot brick yours
up, there are a few things you can do. Second best would be two layers of double glazing
with as much space between them as possible. What? You don't want to make structural
changes to your house/flat (or can't, as the owner might object)? Then make sure the
window seals properly - airtight. Draft excluder around the edges of any opening widows
should help immensely. You can fill the space with sandbags and board up the window if you
can do without the light.
Doors
Well, you shouldn't brick/board up your door for the obvious reasons
(unless you plan on spending a LOT of time in the studio). But they do leak a lot more
sound than the walls, so you have to do something. Indoor doors are usually hollow
lightweight jobs, so get yourself a good quality solid wood outside door. Make it as
airtight as possible against the frame with draught excluder, paying attention to the
bottom of the door too. It may seem like a good idea to have two doors (and for isolation,
it is). However, you won't be able to open two airtight doors (repeat after me -
"vacuum") without something to break the airtight seal, and that would obviate
the effectiveness of having two doors. Some people recommend two sliding heavy glass
doors. Oh yes - don't forget to eliminate any keyholes too.
Floors
Not much you can do here without some construction. Ideally, you would float a
wooden floor above the existing one, with a layer of fibreglass or rockwool between them.
Carpet with underfelt will help dampen some of the vibrations slightly (and also help
control the room's reflections). Mounting amps and speakers on stands which are resting on
layers of rubber or other damping material such as cork will also help dampen the sound
transmitted to the floor and thus, the rest of the house. Of course, there is the option
of using direct recording amps such as the POD or the Roland Virtual Amps. This eliminates
the amp problem entirely.
Ceiling
Two things you can do here. The first is essential - seal the edges of the
ceiling with caulk (silicon sealer) to make it airtight. The second thing is to suspend a
second ceiling below the first, using 'Z' channelling to decouple it as much as possible
from the first. Make sure your second ceiling is well sealed too.
Holes
Seal any holes between rooms. This may seem obvious, but sometimes two
power outlets opposite each other on either side of a wall will share a single hole.
Beware too of airbricks which are common for ventilation purposes.
Ventilation
We've just spent a while discussing how to make your room airtight for the
purposes of acoustic isolation. Obviously you do need to breathe too! A proper studio
ventilation system is very expensive. So you'll have to open the doors between takes
instead. A simple air conditioner will make the room a lot more comfortable to work in
providing you remember to open the doors from time to time. Remember also that an
important function of ventilation is cooling, both for you and your equipment. |
