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      09-10-2012, 11:45 PM   #23
rjd598
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Quote:
Originally Posted by GTM_Challenge View Post
Here is a basic guidline for decibel testing for most state an other testing agencies. We use the same process when we decibel test our exhausts.




Put on ear protection. Stop the vehicle on a solid flat surface and leave it running. Prepare a noise testing spot that is at least 25 feet away from any building or enclosed fence wall to avoid echo.


Place the microphone of a decibel meter even with the level of the center of the muffler exhaust opening. Locate the microphone 19 1/2 inches behind the tail pipe at a 45-degree angle to the opening. The microphone cannot be in the direct gas path from the exhaust.


Set the decibel meter weighting for human ear frequencies, not the low frequency setting used to measure music. Several meters use "A" for ear frequencies and "C" for lower frequencies. Set the decibel range for the legal limit. That sets the maximum sound allocation in the center of the needle sweep on the meter. Most localities set an absolute maximum between 90 and 100 decibels. Set the timing for either fast or slow for metering exhaust sound.
Thanks for letting us know I was always curious as to how this was conducted
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      09-12-2012, 10:05 PM   #24
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Great idea -- waiting to see some more numbers
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      09-12-2012, 10:42 PM   #25
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i'd like to do this but how accurate will it be if anybody miraculously goes above 100 decibels

another note... i read somewhere the iPhone microphone is only god for up to 110 decibels. my exhaust is loud... promise it will go above 100 decibels on cold start on on acceleration.
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      09-12-2012, 11:09 PM   #26
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Quote:
Originally Posted by E90///M3` View Post
i'd like to do this but how accurate will it be if anybody miraculously goes above 100 decibels

another note... i read somewhere the iPhone microphone is only god for up to 110 decibels. my exhaust is loud... promise it will go above 100 decibels on cold start on on acceleration.
Give it a shot and let us know. If its past 110 then well know you have a loud ass exhaust! Hahaha I originally said I know this app might not be the best measure but since it's free and on iPhone we could all use it as a basis. No one would go out and buy decibel reading equipment or even pay for the decibel reading apps so this is our best option.
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      09-12-2012, 11:14 PM   #27
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Quote:
Originally Posted by rjd598 View Post
Give it a shot and let us know. If its past 110 then well know you have a loud ass exhaust! Hahaha I originally said I know this app might not be the best measure but since it's free and on iPhone we could all use it as a basis. No one would go out and buy decibel reading equipment or even pay for the decibel reading apps so this is our best option.
i will but i'll try it the way you describe how to do it as well as how GTM_Challenge describes.

pictures would be best but let's see what i can come up with when i get back from SF on Sunday.
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      09-14-2012, 11:43 AM   #28
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I just ordered the iPhone 5 this morning and they claim the new iPhone has improved audio. Not sure if it would give results different than the 4s I was using but I'll redo my test to make sure there are no differences
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      10-03-2012, 09:03 PM   #29
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Cold Start: 100db

Idle: 90db
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      10-04-2012, 11:05 PM   #30
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RPI ver.1 with Turner Test Pipes

Cold Start Outside:


Cold Start Inside (Windows Up):


Warm Idle Outside:


Warm Idle Inside (Windows Up):
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      10-04-2012, 11:09 PM   #31
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akrapovic gt4 full ti exhaust with ess vt2-625
103.7db measured (black flagged) at Atlanta Motorsports Park

with the catted evo my sound was only at 92db

thats a 16x difference!
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      10-04-2012, 11:10 PM   #32
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I'm going to add inside readings as well this weekend. Should really add depth to this database. I also decided to make a spreadsheet and just continuously update the sheet whenever someone adds new info. Ill place the sheet in my first post
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      10-05-2012, 02:25 AM   #33
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Quote:
Originally Posted by 4sevens.com View Post
akrapovic gt4 full ti exhaust with ess vt2-625
103.7db measured (black flagged) at Atlanta Motorsports Park

with the catted evo my sound was only at 92db

thats a 16x difference!
at what rpm
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      10-05-2012, 06:01 AM   #34
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Quote:
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at what rpm
close to WOT 8k rpm
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