by Arthur Noxon, PE, Licensed Acoustic Engineer
The home theater subwoofer can become
a neighborhood noise pollution problem. You’ll know if you
get phone calls that interrupt your late night movies. Lawnmowers
and leaf blowers may be the scourge of noise pollution during the
daytime but late at night, it’s the subwoofer.
When building or remodeling a house
to include a home theater, some consideration needs to be given
to soundproofing. There are two types of soundproofing. One is for
the interior of the house, keeping explosive noise from upsetting
others in the house. Typically the kids are up late on the weekends
showing movies or playing video games and the parents are trying
to get some reading done.
The second and less considered soundproofing
is neighborhood noise pollution. It’s when your system is
keeping the neighbors up. You can always turn it down but then,
the energy in the movie thins down and the fun of it dwindles.
The best time to do soundproofing is
during construction. Trying to do it after the house is finished
is at least nearly overwhelming and at best, a very expensive and
inconvenient remodel project. The best time to do soundproofing
is well before you actually need it, during construction.
noise levels inside a home theater easily register 85 dB,A and more.
If the home theater is in a concrete basement with no windows and
the whole house on top the theater, then there is little noise leaking
out into the neighborhood. However if the home theater is in the
second story of the wood frame garage add-on then neighborhood noise
will likely be a problem.
wood frame house with a subwoofer in a room with exterior walls
will leak enough bass through the wall to generate about 70 dB,A
at the exterior surface of the house. Stepping back about 5 feet
leaves a noise level of about 66 dB,A. Sound drops in intensity
6 dB for every doubling of distance. Of course on the other side
of the house it’s much quieter because the house acts as a
sound barrier. The following chart shows how loud the bass noise
is on either side of the house at various distances.
People generally will not want to be
hearing the neighbors bass boom at a level more than about 25 dB,A
in their bedroom. This means the bass boom of about 30 to 35 dB,A
outside is likely tolerable. Clearly neighboring houses that lie
within 300 feet of the exterior walls of a room that contains a
subwoofer are likely to have a problem with late night movies.
Copyright 2009, Acoustic Sciences
Corp. This article was written by Arthur Noxon, a licensed Acoustical
Engineer. He is president of Acoustic Sciences Corp and the inventor
of the original corner loaded bass trap, the TubeTrap. He has over
35 years professional experience in acoustics, with the last 20
years specializing in blending the art and science of both acoustics
and psychoacoustics into the listening experience. He may be reached
at firstname.lastname@example.org or by phone: 1-800-ASC-TUBE.