reza@ihuxb.UUCP (07/05/83)
Is there an easy way of sound-insulating the interior walls of a house? My brother-in-law used fiber glass in his house. And then styrofoam comes to mind. But is there something more effective and/or cheaper? H. Reza Taheri ihuxb!reza IW 2C-136 x1040
gjphw@ihuxm.UUCP (07/07/83)
A recent article asked for further information about ways to sound
insulate the interior walls of a house. This is a short tutorial about
sound insulation.
Recently, I purchased a house which was built by the owner. In an
attempt to add sound insulation, the owner insulated the interior walls
the same way the exterior walls were insulated: 3.5 inches of fiberglass
batt. Predictably, this had little effect on the sound transmission
properties of the walls. Thermal insulation is most efficiently realized
using materials that contain lots of air pockets (e.g., fiberglass, styrofoam).
Sound insulation can only be achieved by using construction techniques that
use no air (e.g., a good vacuum between the walls). These two objectives are
somewhat at odds.
Thermal insulation is intended to retard the heat flow between two regions
of different temperatures (e.g., inside and outside of a house). The least
expensive technique to accomplish this involves installing materials that
prevent conduction and convention. With their low specific heats and many
trapped air pockets, fiberglass batt and styrofoam are inexpensive choices.
About the most effective, and costly, means of thermally insulating two volumes
requires a vacuum (i.e., a thermos bottle or Dewar vessel).
Since sound requires a medium for its travel, a vacuum provides the most
effective insulation against it. Unfortunately, a vaccum is still quite
expensive to produce or maintain under normal conditions (e.g., a household).
The second approach to sound insulation uses very heavy construction materials.
While the energy contained in sound is not lost, heavy materials absorb part
of this energy, reflect some, and retransmit some at lower frequencies. These
lower frequency sound waves, often inaudible, are less objectionable than the
original. Also, sound absorbing surfaces, which are designed to trap sounds,
can reduce the sounds that escape from the room in which they are generated
and thus reduce the background sound level in the entire house.
So, in summary, if you want to keep in the heat, use fiberglass or
styrofoam. If you want quiet, build with heavy walls, use sound absorbing
materials on the walls, and don't build the house near a highway.
Patrick Wyant
Bell Labs (Naperville, IL)
*!ihuxm!gjphwparnass@ihuxf.UUCP (07/08/83)
To attenuate the transmission of noise through a wall, one might try hanging a decorative rug against it. Robert S. Parnass Bell Laboratories Naperville, Illinois ihnp4!ihuxf!parnass
leichter@yale-com.UUCP (Jerry Leichter) (07/10/83)
The easiest/cheapest way to soundproof is probably to put up heavy drapes of some sort. You can also go with commercially-available sound-proofing tiles. One important factor often overlooked: It is MUCH harder to keep sound OUT of the room that you want quiet than it is to keep it IN the room where it is being generated. Once the sound has made it to the walls, it can be transmitted by a large number of routes, some of which, like vibration of the supporting 2 by 4's in typical construction, are just about impossible to do anything about. There is just about nothing you can apply directly to the wall in the "quiet" room that will do much good. Drapes will help only because they will be away from the wall - creating a new "noisy room" between wall and drape. Do NOT use styrofoam!!!!! It is very flammable and gives of very toxic fumes even before it catches fire. You could easily make your home extremely deadly in case of a fire. (There may be some kind of styrofoam around that is specifically meant for construction use; I think I've seen it sold as (heat) insulation. It must be treated somehow to make it safe(r). But run-of-the-mill, cheap styrofoam, I repeat, would be DEADLY.) -- Jerry decvax!yale-comix!leichter leichter@yale
eda@tekid.UUCP (Ed Averill) (07/12/83)
This is a real sore spot with me, so I'll pass a bit
of info along.
There is a real inexpensive way of getting great
reduction in sound conduction. It is to use "offset studs".
The standard sheetrock wall surfaces are placed on studs that
do not connect through the wall. This is most easily done in
standard construction with six inch plates at the top and
bottom, and with 4 inch studs placed alternately against each
edge at intervals to support the size sheetrock in use. The
effectiveness comes from the low resonant frequency, and the
low Q of a sheetrock resonator. It should be a standard
construction technique for seperating sleeping areas from the
rest of the house, unless there is some other two-wall barrier
like a closet. I also used fiberglass batting on the premise
that it would help disperse high frequency noise. My success
is so complete that sounds from my living room are perceived
to come from the opposite direction in the adjacent bedroom
because the hallway leads around to a door there. While this
is a standard technique in industrial construction, it took
some heavy emphasis to get my home contractor to put it in.
The other sound path that is hard to control is
ductwork. I suspect that the answer there is massive baffles
for low resonance, probably at the center of a star
distribution system. This is the significant path for noise
from one end of our house to the other. I can understand my 3
year old's requests for potty-help if my head is on the sofa
next to the heating duct at the opposite end of the house.
The duct has a straight shot through the central distribution
point to there.
There are good references on this subject in libraries
with architecture schools. I have no memory of book titles I
have read, but I remember clear discriptions of how to solve
the ploblem. The clearest analogy I ever ran into was that of
transmission line theory. The energy must be dissapated
somewhere, and will be reflected where there is significant
impedance mismatch. The logarithmic nature of the ear
requires a lot of attenuation to be effective.
Good Luck.filed01@abnjh.UUCP (07/13/83)
Vacuum is the most effective way to prevent sound transmission. Those wishing to practice with their rock band in places where it would be audible outside of their dwellig place, I suggest the construction of a vacuum chamber to practice inside.
futrelle@uiucdcs.UUCP (07/14/83)
#R:ihuxb:-26400:uiucdcs:10600111:000:241 uiucdcs!futrelle Jul 13 20:48:00 1983 The PLATO music group people have walls covered with flat egg cartons and rug samples in their synthesizer room, and the sound is really impressive. Joe Futrelle ...A useless pathname, such as vaxq!lrncuxz!smurf!blackbox!grunt!futrelle