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From: "Gary Casey" <glcasey@adelphia.net>
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Subject: soundproofing
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<<The box for my ES's insulation had to weigh over 40 lbs.>>

When I was in a spending spree picking options for my kit I, of course,
bought the noise kit.  When I unloaded it I had the same reaction -
incredibly heavy.

Just something to consider - a suggestion from my noise expert friend - rap
on the surfaces you are concerned about and listen for the tone and
persistence.  That gives you a good idea about whether that surface will
resonate at the frequencies of concern.  A dull thump that instantly
dissipates is good; a ringing sound that lasts is bad.  Often a high-density
absorber right at the center of the panel is the most effective.  This
doesn't relate to absorption, but will indicate the degree of
transmissibility.  100 to 200 Hz seems to be the biggest area of concern (As
I recall, middle C on the piano is something like 260 Hz, so that is a frame
of reference).  It is a good idea to perform this test on just about
everything you bolt into the plane as you don't want the primary excitation
from the engine to drive something into resonance.

Gary Casey
ES project - nothing resonates so far...