There has been some question as to the efficacy of my soundproofing attemps and the reults achieved. Here are some numbers, and an explantion of what they mean.

All results were measured under the same conditions using an Extech digital sound meter on the A scale, at the driver's face. While the absolute accuracy should be correct, as I have had this meter calibrated, the repeatability of the results is the most important thing, and this has been borne out with followup testing. The prototype car is a 2002 Suzuka Blue, running full NEO synthetics for all fluids.
All results are listed in decibels.

BEFORE , ...... AFTER

Idle ..... 69 , 58

1st gear redline ..... 93 , 80

2nd gear redline ..... 95 , 82

3rd gear @ 60 mph ..... 84 , 79

4th gear @ 60 mph ..... 81 , 77

4th gear @ 70 mph ..... 84 , 80

6th gear @ 60 mph .... 80 , 76

6th gear @ 80 mph ..... 85 , 80


Since db readings are logrithmic, this is a pretty good reduction. To note, however, is that the high frequencies are dramatically reduced, and the perception of noise reduction is greater than the numbers show. If you have set your speakers on a home theater surround system with the pink noise generator, think about how loud the center channel sounded compared to the subwoofer at the same decibel level, and you will have an idea of what I'm talking about here.

One more test, that I think is valuable, is the coast down from 70 mph. Sound levels were measured under power on a flat road, then the clutch depressed and the engine allowed to idle, and readings taken. This is a good test of the ambient noise from wind and road rumble. It gives us a noise floor to work with. The stock car produced 81 db, and the soundproofed car 76 db under the same conditions.
Compare this to the idle readings and you can see that there is a lot of noise generated from the car simply moving. Of course, with the high performance tires that come with the car, some is tread noise. This car had S02's, and I don't know if the '04 and later cars have a quieter tread, but their baseline is quieter. Wind noise is the bane of this car. At about 75 mph, it becomes the overwhelming issue. But, decibels are not cumulative. In other words, 2 sources of 90 db noise do not equate to higher sound pressure levels, but they can produce two different sounds that you can easily distinguish. By cutting out, or down, some of the cars mechanical sounds, what is left is a lot easier on the ears.

What do you notice? The first thing that will happen if you shift by sound is that you will continually hit the rev limiter. See the first and second gear numbers above and it will be obvious why this happens. Solid shutting doors, increased midbass, no transmission or rear end whine, no more heat from the tunnel or behind the seats, and no launching of noise through the top well. And, if you put your head forward into the calm area behind the windshield, it's pretty nice. Try this even in a stock car and notice the difference. The decibel reading doesn't change at all there, but it is a lot more pleasant out of the windstream. You can really hear the radio, and you don't have to yell at the passenger. In hot climates the AC will work a lot better because of the heat blocking, and the increased insulation factor in the doors and floor.

You can get the same results. Check out my group buy. I posted this here to give a little more information about the numbers, and to explain to the critics why it really does work. Thank you for reading.