[DeTomaso] Famous Pantera 2000 RPM exhaust resonance

[Pantera Place]

As I've driven the Pantera more, I realized just by ear that the impact of
the sound deadening work that I did was having a larger impact than I first
thought.   It definitely had an impact on engine mechanical noises, but it
also seemed to be impacting the exhaust noise.  

To get a more precise measurement of the situation I did more DB sound level
testing today.  The idle DBa five feet behind the car it still in the 86 to
87 ranges, but to my surprise the interior sound is substantially reduced.
The interior sound level at idle was 86 now it is about 80 (windows down)
and around 75 with both windows up.  

Underway (windows down) in the 2000 RPM range it was 86 and now it is around
80.  Windows up about 75.  What is most interesting the 2000 RPM harmonic
doesn't really sound much quieter by ear.  Expect this is because the DBa
filter does not pick up the low harmonic frequency like the DBc filter
would.   Each 3 DB represents a doubling of the sound level.

The windows up and down readings have a larger delta than they had before.
The exhaust sound seems more remote now and external from the interior.
This was all accomplished just by sheeting the back side of the removable
fiberglass firewall cover with sound deadening material.  My car has the
factory sound deadening material on both sides of the firewall but the
engine hatch is aluminum with no deadening material.   

After I've run the sound deadening material for a while I'll be able to
provide more information on its adhesion to the fiberglass, suitability,
etc.  

Mike