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Old 02-25-2009, 03:20 PM   #7
Vez
Tri-State Training Wheels
 
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Join Date: Aug 2008
Location: Near Philly, PA
Member #8445

My Ride:
2007 UGM Subaru Impreza WRX STI Ltd. #081/800

iTrader: (0)
First Set of dB Readings

So, thanks to rexbro, (thank you again) he leant me his dB meter. I was able to complete some of the dB testing; I plan on finishing the tests tomorrow.

In accordance with the site, meter, and general test conditions as described in Title 67 pf the PA Vehicle Code, I took measured dB levels of my car. After completing tests on gears 1-3, I have proven that I would need to hit at least 6000 rpms in each gear to be in violation. Consequently, there is no possible way that I was even close to being in violation under normal driving conditions. The car can be and is, easily driven under the legal noise levels. I would need to be shifting past 6000 RPMs in at least the first 3 gears, to be in violation of the law.

As a reminder, on a hard site, driving 35 MPH or less, the legal dB level is 78 or less...driving >35 MPH, the limit is 84 dB.

Test Conditions:
10:00AM, intermittent 10mph WSW winds (which is within the test parameters), 54 degrees F, 71% humidity, Ambient Noise Levels: <50dB.

The following numbers are in the format (RPMs/MPH/dB).

1st Gear: (1000/<5/58), (2000/6/62), (3000/16/70), (4000/22/72), (5000/26/75), (6000/33/80)

2nd Gear: (1000/~7/60), (2000/18/63), (3000/25/71), (4000/35/76), (5000/42/78), (6000/51/84)

3rd Gear: (2000/26/67), (3000/38/74), (4000/51/79), (5000/63/82), (6000/75/85)

4th Gear: (2000/34/68)

Based on this preliminary data:
driving 45 MPH in 2rd gear produces ~78 dB.
driving 45 MPH in 3rd gear produces ~76 dB.

One can assume the driving 45 MPH in 4-6 gears will produce even quieter results.

I tested 10 different passing vehicles (in a 45 MPH speed zone). The dB average of these vehicles was 71 dB. Normally, going 45 MPH, I'm either in 4th or 5th, which gives me better gas milage. That would put me around 73 dB...louder than the average, but by only 2 dB. Limit...84....me ~73, WELL within my legal rights and far from the legal limit giving no cause to suspect an illegal exhaust. Additionally, you can see that if I were in stop-and-go traffic or low-speed traffic, I would probably be either 2nd or 3rd gear...while these may be approaching the noise limits, they are still well within the limits, and thus, legal.
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