Estimating exhaust volume (dB) - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

halfwaytobedlam · 04-03-2021, 12:13 AM

I admit this is a bit silly, but is there anyway to estimate how loud an exhaust will be (eg mathematically) to meet track noise limit requirements? I've tried using sites that estimate dB at a distance but it doesnt seem right. For example:

According to FR-Sport (https://bit.ly/2PnkruJ), they measured Tomei 60r (no other mods) at 107db @10'. Therefore according to this physics site (https://bit.ly/2PT5sZ0) it would be 92.1 db @ 55 feet, which is apparently just over the noise limit at laguna.

Then again someone with a Buddy Club Spec II measured 95.8db @ 100 feet by a autocross marshall. which would mean it would be 115db @ 10' LOL

Does this make sense to you guys?

Yoshoobaroo · 04-03-2021, 09:07 AM

Yes it makes total sense. Both those exhausts are loud as duck, and Laguna Seca has fairly strict limits compared to other tracks.

As for estimating it, not really. Sound pressure will not stack predictably with other mods, and it can come down to even which exhaust hangers and how many you're using. Measuring is the only real way.

ls1ac · 04-03-2021, 01:22 PM

Further, it does not act as a point source. So radiation pattern is not even and equal.

humfrz · 04-03-2021, 04:06 PM

Yep, when your SO yells that "your exhaust is so loud, I can't even hear the radio" - that is too loud.

halfwaytobedlam · 04-03-2021, 09:56 PM

Thanks everyone, I knew the estimation calculation results were too good to be true haha. Guess i'll focus on other areas of the car for weight then

Lantanafrs2 · 04-03-2021, 10:11 PM

The look on your neighbors face is as good as any db meter.

jflogerzi · 04-04-2021, 03:54 AM

Quote:

Originally Posted by halfwaytobedlam

Thanks everyone, I knew the estimation calculation results were too good to be true haha. Guess i'll focus on other areas of the car for weight then

Most guys run stock muffler at that track. You can also look for a higher dba limit event but they cost more $$

Sent from my GM1915 using Tapatalk

re-animator · 05-06-2021, 07:04 PM

you can get a silencer for the t60r and t80r. just put in the silencer if you are on a track with strict limits. not ideal for power but butter than being sent home.

BRZoomTX · 05-07-2021, 09:45 AM

Quote:

Originally Posted by humfrz

Yep, when your SO yells that "your exhaust is so loud, I can't even hear the radio" - that is too loud.

That is when you simply tell them to turn up the radio.

TommyW · 05-07-2021, 10:10 AM

If you had a car with more power you could lift at the tower but with an 86 you’ll be crawling up to T6

humfrz · 05-07-2021, 12:12 PM

Quote:

Originally Posted by BRZoomTX

That is when you simply tell them to turn up the radio.

You been married long?

04-03-2021, 12:13 AM	#1
halfwaytobedlam Member Join Date: Nov 2020 Drives: 2014 Toyota 86 GTS Location: Northern Territory, AUS Posts: 10 Thanks: 2 Thanked 5 Times in 3 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Estimating exhaust volume (dB) I admit this is a bit silly, but is there anyway to estimate how loud an exhaust will be (eg mathematically) to meet track noise limit requirements? I've tried using sites that estimate dB at a distance but it doesnt seem right. For example: According to FR-Sport (https://bit.ly/2PnkruJ), they measured Tomei 60r (no other mods) at 107db @10'. Therefore according to this physics site (https://bit.ly/2PT5sZ0) it would be 92.1 db @ 55 feet, which is apparently just over the noise limit at laguna. Then again someone with a Buddy Club Spec II measured 95.8db @ 100 feet by a autocross marshall. which would mean it would be 115db @ 10' LOL Does this make sense to you guys?

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04-03-2021, 04:06 PM	#4
humfrz Senior Member Join Date: May 2013 Drives: 2013 FR-S, white, MT Location: Puyallup, WA Posts: 29,868 Thanks: 28,790 Thanked 31,815 Times in 16,425 Posts Mentioned: 708 Post(s) Tagged: 2 Thread(s)	Yep, when your SO yells that "your exhaust is so loud, I can't even hear the radio" - that is too loud.

04-03-2021, 09:56 PM	#5
halfwaytobedlam Member Join Date: Nov 2020 Drives: 2014 Toyota 86 GTS Location: Northern Territory, AUS Posts: 10 Thanks: 2 Thanked 5 Times in 3 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Thanks everyone, I knew the estimation calculation results were too good to be true haha. Guess i'll focus on other areas of the car for weight then

04-03-2021, 10:11 PM	#6
Lantanafrs2 Senior Member Join Date: Jan 2018 Drives: 2013 frs red Location: South Florida Posts: 3,517 Thanks: 2,520 Thanked 3,088 Times in 1,654 Posts Mentioned: 6 Post(s) Tagged: 1 Thread(s)	The look on your neighbors face is as good as any db meter.

05-06-2021, 07:04 PM	#8
re-animator Senior Member Join Date: Jul 2017 Drives: 2013 BRZ Location: San Diego Posts: 213 Thanks: 135 Thanked 83 Times in 45 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	you can get a silencer for the t60r and t80r. just put in the silencer if you are on a track with strict limits. not ideal for power but butter than being sent home.

05-07-2021, 10:10 AM	#10
TommyW Senior Member Join Date: Feb 2017 Drives: '13 Whiteout Location: San Clemente Posts: 1,491 Thanks: 496 Thanked 1,242 Times in 673 Posts Mentioned: 10 Post(s) Tagged: 0 Thread(s)	If you had a car with more power you could lift at the tower but with an 86 you’ll be crawling up to T6

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