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darcane · 02-05-2014, 05:10 PM

So, I've gotten some flak about my straight pipe being obnoxiously loud by a couple people on this forum. However, none have actually heard it and I believe that it is OK as is. So, how to verify?

SAE J1169.

This is the very specific standard for measuring the sound level of a light passenger vehicle's exhaust. The test is performed at 75% of the engines peak horsepower rpm, about 4500 for my Civic. The sound level meter must be 0.5m(20") from the exhaust outlet 45° from directly behind the outlet. The sound level meter must be parallel to the ground at the same height as the exhaust tip, but no less than 0.2m (8") from the ground. It should be in a wide open area with no wind, and no surfaces to reflect sound back to the meter and tested using an "A" weighting on the meter. I did my best to eliminate all other variables, but I did have some wind today.

Numbers:
Each measurement was made three times and averaged.

At an idle, I measured 73dB
At 2500rpm, I measured 94dB
At 4500rpm, I measured 97dB

OK, so is it legal? Well... no. WA state actually has no noise level requirements, it just states that you must have a muffler and it must not be any louder that stock. So, really any aftermarket exhaust is illegal per state law. Most states that do have a limit, put it at 95dB, and I am right on the border of that. As I drive this car for economy, I believe this is the first time I've had this engine at 4500rpm. I normally shift between 2000 and 2500rpm, so it is below the generally accepted levels in my normal rpm range

So, is it louder than stock? Yes.
Is it loud enough to bother other people? I'm comfortable saying no here. And I have no concerns about getting ticketed for it.

Especially since the farther away you get, the quieter it is. As you can see, the reading is taken very close to the exhaust outlet, and sound levels drop quickly with distance as it follows the inverse-square law. Just 5 feet away, it drops down to 62dB at idle. That's less than half as loud and about the same sound level as a normal conversation. While testing I was able to tell my F-I-L commands without needing to yell, and I felt no need for hearing protection while observing the sound level meter.

02-05-2014, 05:10 PM	#52 (permalink)
darcane ......................... Join Date: Aug 2009 Location: Buckley, WA Posts: 1,597 Thanks: 391 Thanked 488 Times in 316 Posts	So, I've gotten some flak about my straight pipe being obnoxiously loud by a couple people on this forum. However, none have actually heard it and I believe that it is OK as is. So, how to verify? SAE J1169. This is the very specific standard for measuring the sound level of a light passenger vehicle's exhaust. The test is performed at 75% of the engines peak horsepower rpm, about 4500 for my Civic. The sound level meter must be 0.5m(20") from the exhaust outlet 45° from directly behind the outlet. The sound level meter must be parallel to the ground at the same height as the exhaust tip, but no less than 0.2m (8") from the ground. It should be in a wide open area with no wind, and no surfaces to reflect sound back to the meter and tested using an "A" weighting on the meter. I did my best to eliminate all other variables, but I did have some wind today. Numbers: Each measurement was made three times and averaged. At an idle, I measured 73dB At 2500rpm, I measured 94dB At 4500rpm, I measured 97dB OK, so is it legal? Well... no. WA state actually has no noise level requirements, it just states that you must have a muffler and it must not be any louder that stock. So, really any aftermarket exhaust is illegal per state law. Most states that do have a limit, put it at 95dB, and I am right on the border of that. As I drive this car for economy, I believe this is the first time I've had this engine at 4500rpm. I normally shift between 2000 and 2500rpm, so it is below the generally accepted levels in my normal rpm range So, is it louder than stock? Yes. Is it loud enough to bother other people? I'm comfortable saying no here. And I have no concerns about getting ticketed for it. Especially since the farther away you get, the quieter it is. As you can see, the reading is taken very close to the exhaust outlet, and sound levels drop quickly with distance as it follows the inverse-square law. Just 5 feet away, it drops down to 62dB at idle. That's less than half as loud and about the same sound level as a normal conversation. While testing I was able to tell my F-I-L commands without needing to yell, and I felt no need for hearing protection while observing the sound level meter. __________________ Past Cars: 2001 Civic HX Mods CTS-V 2003 Silverado Mods