so my brother brought home a decibel meter tonight...
 

sooo we measured my exhaust level. now i've always found it pretty reasonable. the magnaflow catback tames things down. anyway, here's my findings:

the legal exhaust limit level is rediculous! we measured my exhaust by approximate legal specifications. 20 inches away at a 45 degree angle.

at IDLE my exhaust exceeds the legal limit by 1 decibel. from inside the car i can't even hear it. at 4500rpm(legal measurement is done at approximately 3/4 speed of where engine makes peak hp) it measured 126.3 decibels. approximately 8-9 times the legal limit. 5000+ rpm probably would've exceeded the meters range.

that law is rediculous haha. good thing it's not strictly enforced. thought some of you might find it interesting.

What was my reading again?

You have headers, ory and an exhaust and you can't hear it inside your car? Either you are deaf, or a liar. Which one?

bring it by my house next time

What kind of meter are you using?

agreed:nod:

You sure it's 20 inches?

SAE test procedures is:

The Society of Automotive Engineers (SAE) with an established noise limit of 95-decibels (SAE J1169). Under the SAE standard, a sound meter is placed 20 inches from the exhaust outlet at a 45-degree angle and the engine is revved to three quarters of maximum rated horsepower. The highest decibel reading is then recorded...

maybe 20 feet?

everything online says the test is done at 20 inches, idkkk. we did 20 feet at first and i was still at 115. then we looked up the actual test online and that's what it said.

at IDLE i can not hear it inside the car. i am neither.

115 or something

no point, only reads to 130 decibels, which btw is typically considered the point of pain and hearing loss haha

Phonic PAA2

The reason why I called bs is the fact that I could hear my car at idle with just a magnaflow exhaust... Had one there for 2 years or so. :shrug:

well yeah i mean you can hear it if you're listening, but between the radio, power steering pump, and valvetrain noises, it's not really like wow the exhaust is loud. with the radio off you hear it, but under normal circumstances it's not very noticeable. maybe i'm just used to it.

Everyone's forgetting to ask, what kind of decibel meter? I'm sure the quality of the product can affect the results

Reading ftw. :wink:

You mean like post #5 when i asked what meter? lol I crappy walmart meter will read a lot higher than the real numbers.

:nod: much like that haha

If your power steering pump and valve train are louder inside the car than your exhaust setup, its time for some maintenance

honestly, nothing in the engine bay makes very much noise at all. exhaust just really isn't very loud at all at idle. you can hear the pump so that will be replaced soon, but the minimal amount of valvetrain noise that i have is nothing out of the ordinary.


my original post was a slight exaggeration, you can hear it. my point was just that if that really is the legal limit it is stupidly quiet, and absolutely any aftermarket exhaust greatly exceeds it. really i don't see why everyone thinks longtubes automatically means insanely loud. automatics idle at 550 and through a magnaflow even with longtubes it is very very tame.

how long do you think you'll have that decibel meter, til Oct 17 maybe?

forever, it belongs to the school aka my brother

i, for one, found this most entertaining. informative, even. so maybe all of those cops are right and we're wrong? the exhaust really does exceed SAE standards? wow*. just... wow.



but outside of the law, according to your anecdote.

*btw, there is zero sarcasm in my reply. i know it's hard to tell with typed words what the mindset is of the typist, but i can assure you i meant no sarcasm at all.

My car is quieter than Keiths, which unless you really get on it isn't very loud. I got pulled over for "loud muffler" a week ago, let off with a warning [knock on wood], but my car only made "115 or something" when we tested it on Keith's db meter (that was at redline too).

jims69camaro, i really don't understand exactly what it is you're trying to say. when i said i exaggerated, i was saying that it is indeed audible but barely so at a idle. i knew ahead of time my exhaust was illegally loud higher up. what i've been saying about the law being insane is that at IDLE my car exceeds the sound limit for any rpm, and from inside the car it really is barely audible. if anyone cares to dispute this i will gladly let them sit in my car and listen for themself.

at higher rpm my car is loud. very loud. i was expecting it to be illegal, no surprise there.

FWIW, I had my town's cops check through the books, they couldn't find any actual decibel limit

I would have to check again to be sure, but IIRC, NJ motor vehicle code specifies the SAE test outlined earlier in this thread to check. I have heard from numerous cops that it is left up to the officers discretion, and this may be due to local ordinances.

- Justin