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 THE
BASICS:
When solving a noise problem,
you need to establish a few things:
1) Is the noise coming from within this space or is
it coming from an adjacent space?
2) How loud is the noise in dBa (Decibels) Radio Shack
sells a sound level meter for about $60, its not a very
good one but it will put you in the ball park.
3) How loud would you like it to be. Keep in mind that
most homes and office spaces are at or about 35 to 45
dBa to begin with. Dead Silence is not a reasonable
goal.
Now for some answers:
If your noise source is in another room and you'd like
to keep it there, you need to increase the transmission
loss (TL) of the materials that make up the partitions
between the rooms (i.e.,drywall, plaster, doors, windows).
Products that increase the TL of a partition are rated
with an STC (sound transmission class). Be very careful
when looking for "Sound Proofing" products
that do not give you an STC rating if you want them
for increasing your TL. Some products will be rated
with an NRC rating. The NRC rating is something completely
different and is part of the most commonly misunderstood
functions of acoustics. Sound Proof Foams are also usually
a misrepresentation. In order to increase the TL of
a partition, you must increase it's mass. Closed cell
foam and spray on material don't do this. That's not
to say that they don't have their place in acoustics.
They just don't work for this problem. Look for products
that have an STC rating of STC 26 or higher. Some of
these may be a loaded vinyl barrier that weighs 1 or
2 pounds per square foot. Another great material is
good old fashioned drywall. Adding an extra layer of
drywall to an existing wall (as long as there are no
holes in it) can make a dramatic improvement. You can
kick it up a notch by mounting the drywall on isolation
clips (try to stay away from resilient channel, it's
to easy to short circuit).
Another thing to remember when buying soundproofing
materials on the Internet is that you're dealing with
a company that could be anywhere. Make certain that
their website shows you who they are, where they are,
and how to contact them via other means than e-mail.
You should be able to call and speak to someone if you
have questions. Soundproofing Stuff isn't cheap - don't
be afraid to get help.
Matt Oeler
President
Oeler Industries, Inc.
So you've decided you're going to invest in some home
theater equipment. You head off to the dealer's showroom
and are blown away by the top of the line system and
lay down $5000.00 bucks and head home. Brimming with
excitement, you spend hours mounting and installing
everything until the big moment when yor drop in your
favorite DVD only to find that you are missing the smooth
and dramatic response you heard at the store. So what's
missing?
The bottom line is that once you've reached mid-range
quality in your AV equipment, the weakest link is going
to be the room acoustics, the most overlooked aspect
of setting up a home theater. When you are more than
a few feet away from the speakers, you are listening
from what is called "far field", and the sound
is actually coming to you indirectly from the room and
not the speakers. Because the speakers are spreading
sound in many directions, the room acts like a big filter,
exaggerating some sounds while softening others.
Now where do you start? If it is within your budget,
it would be well worth the investment to hire a professional
acoustical consultant, but if you need to keep your
costs down, you can certainly improve your room acoustics
by following a few simple rules:
- If possible address any excessive
outside noise, (HVAC, traffic, footsteps, etc.).
- Treat 20% to 40% of your wall space
with acoustical absorption panels to reduce reverberation,
flutter, and echoes.
- Add absorptive bass traps to corners
to reduce low frequency build up.
There are many noise control products to keep unwanted
sounds from entering your home theater. Duct Silencers
and pipe and duct lagging to reduce HVAC noise, vinyl
noise barrier and isolation clips to decouple walls
and ceilings thus interrupting the transmission of sound
waves, as well as acoustic doors and door seal kits.
The goal here is to improve speech intelligibility in
the movie's soundtrack by lowering the signal to noise
ratio (that is, the relative strength of the speech
vs. the background noise).
Acoustic panels and bass traps come in a wide variety
of materials and price ranges. There are custom fabric
wrapped panels that can be made to seamlessly integrate
with the room's décor, as well as prefab panels
and out of the box kits. The main thing to remember
is that a mediocre sound system in a well-tuned room
will outperform a top of the line sound system in a
poorly tuned room.
Jack Kress
Oeler Industries, Inc.
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