| Ok, for everyone who has an opinion about soundproofing the Z, I have done the research, and now can offer definative results. I took my stock 91 N/A with 178,000 miles (all original and noisy) removed the entire interior, and made the following modifications/improvements:
Installed 70 sq. ft. of Brown Bread (Dynamat Extreme equivilent)
Installed 40.5 sq. ft. of V-Comp (Sound barrier) Filled most gaps in the body panels with 8 cans of Dap-Tex expanding latex foam Sprayed 6 cans 3M rubberize undercoating on the inside of the wheel well spalsh guards (top and bottom sides) Installed new window seals and adjusted window height. Removed and reinstalled windshield wipers to stop lower when turned off.
Below are my results using a calibrated sound meter measuring 50-115 decibels using both A and C algorithms (weights). Measurements were taken before and after at various speeds, as noted below. The first number is the before with the stock interior installed, the second if after with the stock interior reinstalled.
"A" Algorithm "C" Algorithm Off/Parked 52 <50 58 <50
On/Parked 58 52 80 75.5
15 MPH 68 64.5 91.5 85
30 MPH 71.5 66.5 93 88.5
45 MPH 73.5 68.5 94 89.5
60 MPH 75 71 96.5 92
75 MPH 78.5 73 100 93.5 Average Change 4.857 5.857
It should be noted the decibel scale is logarithmic in that a 3db increase represents 2x the level of sound energy, and sound level perceived. The average decrease in sound level across the spectrum calculates out to 5.357 decibels. Also, with the materials used, the soundscape has changed dramatically dampening most sounds audible to human perception.
As far as how it "sounds"... the sounds of the car are much more comfortable. Before if you passed 3k RPMs the car would sound as if you were trying to race it with all the exhaust noise and sounds coming from the body of the vehicle. Now, I find myself reving to 4.5k RPM before I even notice it, and the sound is very smooth and you do not even hear the exhaust. I notice a definate increase in the SPL and the quality of sound from the stereo is far superior even without an amp. Also to be noted is while talking on the cell phone (fairly sensitive microphone) most background noise has been eliminated, and the person on the other end (who I have test with before) indicates the car sounds as if I am going 20-30 MPH, when in fact I am going 60.
Now, the down side... this project will add approiximately 65-70 pounds of weight to your Z car, while setting you back approximately $350-$400. If you do not have at least 15-20 hours to spend on this project, do not even try it, as you would not come close to finishing it.
As far as my opinion goes... the Z will never be as quiet as a Mercedes Benz, but this will definately make a noticable inprovent in the "quality" feel of the vehicle. It also greatly reducing driving fatigue not to mention the fact you do not have to have the radio cranked up just to hear your music. On a scale of 1-10, I give this project the following ratings: (the higher the better)
Time 5
Effort 5
Cost 6
Quality 9
Satisfaction 9
Frustration 5
Overall Impression 9 Average 6.86 (Worth doing in my opinion) If anyone has any questions, please feel free to email me directly at jarodtoups@hotmail.com
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20:50:05 01/15/04
