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RE: [T3] Sound Deadening
Wanted to get my 3 cents in here, too.
Going back to Jim's original statement about simply adding mass to deaden
sound/noise. This is still a most effective and cheap way to improve
NVH(Noise, Vibration, and Harshness) of a body structure. The body
structure certainly transmits noise from the road and powertrain, but a very
large contribution to a vehicle's NVH comes from the body structures
generation (maybe amplification would be a better word) of noise. The
large, relatively unsupported, flat body panels have very low natural
frequencies. When these frequencies match frequencies generated by the road
or engine at idle, the panel resonates, adding to the NVH of the vehicle.
This phenomenon is easily demonstrated on the proving grounds track here at
Ford. (BTW, Have I mentioned how cool my job is...? 8^))
One common way of effecting this phenomenon is the ribbing or beading of
panels like the T3 floorpan. This ribbing increases the panel stiffness,
raising the natural frequency at which it is excited. This is fine for the
factory to do and for floor pans, but not very desireable for roof panels
and door skins or for the home mechanic to to do.
The cheapest and easiest way to effect this is to add a heavy mat to the
panel. This also raises the natural frequency of the panel making it less
likely to be excited at the lower frequencies of the engine and road noise.
It has the added benefit of also decreasing the direct transmission of noise
as Jim and Bob explained.
Ok, enough technical babble.......did I mention that the body of my Fasty is
coming off this weekend? and that I pulled the engine and have an engine
stand for it? Which BTW, I have to modify to make it adjust small enough
for the T3 bolt pattern.
Later,
John (that pesky Ford engineer) Jaranson
'71 FI Auto Fasty
http://hometown.aol.com/jaransonT3
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