61 How can I make my car quieter? What kind of sound insulation is available?
Description
This article is from the VW Performance FAQ, by with numerous contributions by Jan Vandenbrande others.
61 How can I make my car quieter? What kind of sound insulation is available?
A:There are a variety of products available on the market
that you either glue on the car's inner body panells or
spray into cavities. These products are available from
either car audio stores, or electronic stores. Do shop
around because price varies alot.
The effects of this insulation varies with the type of
material used and how and where it was installed.
Generally, the more you cover up, sometimes even doubling
up in certain areas, the greater reduction in noise. It
will also improve the sound quality of your car due to
the fact you have lowered the resonance frequency.
VWs generally produce most of their noise in the engine
compartment, followed by the entire exhaust system, the
wheel wells (rear), and after that it's probably a toss
up whether your doors or your roof makes the most noise.
For the more recent models, VW actually did a fairly good
job at insulating the car, however, there is always room
for improvement.
Start with the easily accessible areas that have bare
sheet metal, and that sound "tinny" when struck. Most
people start by insulating the trunk floor, rear wheel
wells, the spare wheel well, and underneath the rear
seat. Those areas are right above the muffler or the
wheels with little or no insulation. In my Corrado G60, I
noticed a reduction in buzzing coming from the rear. The
car is now noticeably quieter in the rear versus the
front, while previously it was about the same. Some have
reported results up to 10 dBa reduction, which is rather
significant (a 3dB reduction = 1/2 the noise).
If you are more ambitious, go underneath the carpets as
well. However, depending on the model of the car, VW
probably beat you to it already and it's unclear whether
it'll make much of a difference.
The next areas to treat are harder. If your car does not
have foam underneath the hood, add it. Next try
insulating the fire wall, but be aware that that area
gets very hot and you need suitable materials for that
area.
The top is like a bloody drum, in some respects, and
anything done here to deaden it or change the harmonic
frequency helps. Note that the foam insulation that vw
uses deteriorates after a period of time, especially the
headliner.
Cut the mats to size, than pull of the adhesive cover and
stick it to the body panel. Some products require a heat
gun (hair dryer works too) to establish a firm bond, or
to get the material sufficiently pliable. Some apply
additional glue, such as 3M "Spray 99 adhesive" to get a
good bond.
Probably the most popular product in the USA is that made
by Dynamat. Another brand name with a similar product is
AccuMat by Scoshe Industries. Both Dynamat and AccuMat
sell a variety of types, the thin sheets are generally
for covering body panels, the thicker for under carpets,
and a high temp mat/foam sheet that can be used in the
engine compartment. Other brand names are: Kentamat,
Sonex, a foam padding, designed much like the walls of
an anechoic chamber, available in various thicknesses and
densities, and used to deaden or absorb sound in rooms,
chambers, or instrument areas.
Dynamat is some kind of asphalt sheet with glue on one
side, while AccuMat is made out of latex and the thicker
ones out of foam. Some speculate that Dynamat is nothing
more than Bitumen roofing paper, and therefore any dense
material would work. Some have had limited success with
using asphalt roofing material such as "Elastophene Flam"
which is an SBF membrane roofing material (it's black,
heavy, fireproof, 1/8" thick and relatively cheap) or
simple vinyl floor tyles which the AccuMat thin product
resembles.
I have used the thin sheets from both Dynamat and
Accumat, and they both have pros and cons. Accumat costs
more, adheres better but does not dampen as well. Dynamat
does not adhere well at all (unless you use a heat gun or
spray on adhesive), dampen better than Accumat
(subjective opinion) but out of the box, Dynamat STINKS
majorly. Applying this fresh dynamat over a surface that
get hot (i.e., above the exhaust system) will noticeable
smell up your car. The problem goes away over time, but
it's better if you leave the sheets to bake and air out
in the sun for a couple of weeks. Dynamat does sell a low
oder version, but that's even more expensive and smaller
than their regular sheets.
ADVOTECH (CA) sells a product called RattleTrap which is
a rubbery goo (it reminded me a bit of Plummers' Putty
actually) you squeeze into cavities that buzz.
Continue to:
My Books
