How far away from the exhaust are people doing these DB readings?

My buddy’s 2015 stock Z/28 blew sound at Laguna Seca @ 93db, but that’s also like 40 feet away from the sound booth.

The inverse square law states that the decibels will drop by 6 for every doubling of the distance

https://en.wikipedia.org/wiki/Inverse-square_law

This would suggest that an exhaust has to be pretty loud at distance to catch the attention of a cop, and that the distance measured from the tailpipe would matter too. The measurement goes like this:

https://itstillruns.com/tell-exhaust-loud-7658380.html

Theres a bunch of youtube videos of people doing a db test and showing the Abarth showing a range of between 98-110 db depending on the video and equipment used.

Donut Media also did a video on the exhaust law and test one of their employees stock Fiat Abarth and they got around the number i mentioned. So yes while these arent official numbers, Donut Media did follow the exact procedure when doing the test (compared to someone standing behind with an iphone) and so i'm inclined to think they were pretty accurate on their findings.

https://youtu.be/xUa1jIVlQ_o?t=383

Thats the video with a timestamp where they test the stock Abarth. Actual number they got was 100db and some change so i was off by two, but fact of the matter is thats still illegal.


The thing is, there isnt a universal sound compliance level. Not really. While most cars stay around the 90db range, a lot of manufactures dont make their cars to apply to this standard because it changes per state and per country. As i stated above, Oregon has a DB limit of 88. And since CA has a noise limit of 95db...who do car manufactures listen to? Thats usually why a lot of these laws come with modifiers. For example, one of the modifiers say that your car MUST have a working muffler. Which again the stock Abarth actually fails because it literally comes from the factory with a muffler delete. And now you begin to see the issue. Because a fully stock Fiat Abarth which can legally be sold in California by Fiat dealers, is immediately not compliant with noise AND exhaust laws in California on the showroom floor.

We have the exact same wording in our laws here. What I have found is that people get so focused on the decibels that they ignore the part of the law that says "unusual noise". Droning fart cans, pops and crackles, whistles and throbbing bass notes can all attract attention no matter how loud they actually are. The point being that it doesn't take volume to attract attention.

Yeah, while DB is a measurment of volume, its acutally more a measurement of the generated energy of sound waves. Perceived volume is what really needs to be focused on here. For a long time i was running UEL catless headers with the Nameless Axelback. 100% over the DB limit, however i never got pulled (and my car was pretty heavily modded too) and i largley think its because the perceived volume of my car was a lot lower than the actual reading.

Point being, even if you are under the db limit, if your car has a ton of pops and rasp and makes a ton of noise that most exhausts dont make, you'll be pulled almost guaranteed.

There might be a db difference between reving a motor and holding the motor at a given rpm. There is also a difference between having the motor rev and having the motor under load because the turbo will be spooling under load and change the note.

It definitely sounds loud (see video below for awesome sounds). Just like how the Euro model has a muffler, I thought the California model might come with a muffler. They obviously make Federal and California emission vehicles, so I figured there might also be different versions too or an exhaust valve like what Mustangs have.

[ame]https://www.youtube.com/watch?v=wfQ73shGGoc[/ame]

I got pulled over the other night on 101 South in SouthSF by CHP. He said he pulled me over for exhaust and made me pop my hood. He didnt find anything. Also mentioned that my car is too low and mentioned something about headlight height from the ground, which i knew about. Didn’t cite me for anything, just gave me a verbal warning and let me off.

Maybe the law has changed since last I looked. The law on lowering used to be that no part of the car can extend below the rims.


Are your rear windows tinted? Cops hate tinted windows, monster chrome exhaust tips and big subwoofers.


The MR2 in my sig was low and loud. I got away with it due to: luck, no window tint, boring looking exhaust tip, but mostly because I look like an old white dentist. :)

Here you go for the headlight law: https://leginfo.legislature.ca.gov/f...ctionNum=24400


No more than 54" high or 22" low.


iirc, Nick has a Tomei type-80. Not the best exhaust in terms of loudness (at 4.5k rpm it's def over 100 db w/o silencer). I have had mine on for about 5 years (catback only and 90% of the time w/o silencer) and have not been pulled over at all for it. I think it really depends on how you are driving and whether or not the LEO is looking for a target.

Im running 5% tint all around and rolled them down once i saw the cop put his lights on. Wasnt speeding at all, i was in the slow lane passing 280 on 101 exiting Paul Ave.

While there definitely is a difference, the problem is that the test for noise compliance is the car stationary and holding revs at the RPMs the car would be at for cruising. Which means the turbo isnt adding any sort of muffler effect which means its louder.

Exactly

That's messed up. Sometimes you do everything right and still get pulled over. Not anything you can do but roll with it I guess.

Did you end up keeping the exhaust on and doing the certification?