Question on prep and road noise reduction before carpet installed.
'78 Midget. Area below feet on both sides, and drive shaft tunnel are covered with a black hard rubber/asphalt that I'm guessing is an original and not very effective sound absorbing material.
Was this stuff used on earlier Spridgets? How effective is it?
When installing newer sound absorption products like Dynamat/B-Quiet/Brown Bread is it better to remove the old asphalt and secure the new stuff right to the metal? ....or is it better to install the new stuff directly over the old asphalt.
I can only guess good reasons to use either method. These products work in at least 2 major ways; They dampen vibration by changing the natural frequency (and harmonics) of the sheet metal (Acoustic Loss Factor - ALF), and deaden the sound waves that do actually transmit thru the metal (Transmission Loss - TL). The manufacturer's instructions show rolling the product on firmly after good cleaning. It is my impression that good adhesion is quite important.
Some of the asphalt on the tunnel sides loose. If new product is laid over loose asphalt seems like it will loose vibration dampening.
However, just like beer 30 years ago, the more the merrier. Therefore, seems that installing new product on top of pre-existing would have a cumulative effect, especially where the original bond is still good.
BTW, Dynamat has the great reputation, but is crazy expensive. B-Quiet/Brown Bread and Dynamat are all tested to the exact same ASTM E756 Standard, identical Hz and temperature. B-Quiet is certified better at almost every Hz and temp, and is only half-crazy expensive.
B-Quiet, 50 sq feet, $109 plus shipping. b-quiet.com
Dynamat, 36 sq feet, $270 plus shipping. dynamat.com
Haven't used either but just ordered B-Quiet. I figured that since the bulk carpet was only $40, I could spend a few $$ on noise reduction.
Looking for the sound killer guru to speak. Thanks in advance.
Blueghost