Exhaust system sound levels requirements

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Ok since this got brought up in another thread in the Vendor section. Some of us are looking at exhaust mods. Some already have mods done. We need to know before the season starts what the rules are so they can be met.

Decibels?
Measured at what distance?
At what rpm are they measured?

What is acceptable sound level?

Graham

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

An example of sound abatement policy from the SCCA Mohawk-Hudson region reads as follows (found via Googling "scca solo ii decibel level"):

i
Due to the sensitive nature of our sport in regard to excessive sound, the following procedures will be followed during the season at sites deemed to be in sensitive locations. For a list of such sites, contact the current Solo II Regional Chairperson.

ii
Maximum allowable decibel limit will be 93 dB.

iii
Initial sound readings will be taken during tech inspection. The purpose of this test is to screen out obvious sound violations. Competitors shall rev engine to 1000 rpm below redline for one or two seconds; a sound reading will be taken 50 feet directly behind the exhaust outlet. If a vehicle does not pass this test, the competitor must make changes to the exhaust system and get tested again, prior to his/her first run. No one may attempt an on-course run until they pass this test.

iv
Any competitor who fails this test and is not allowed onto the course for an official run shall be refunded his/her entry fee.

v
On course sound readings will be obtained at selected events. Any competitor failing this test may not take another run until s/he has made a good faith attempt to rectify the problem. If that competitor's next run violates the sound requirement, they will be disqualified. In the case of multi driver cars, if the car fails the sound test during the first driver's first run, a fix must be attempted before anyone else can attempt a run in that vehicle. If the sound level is still excessive during the next run in that vehicle, the vehicle will be disqualified. Any competitor failing the on course test will NOT be refunded their entry fee.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Graham Jagger wrote:

Ok since this got brought up in another thread in the Vendor section. Some of us are looking at exhaust mods. Some already have mods done. We need to know before the season starts what the rules are so they can be met.

Decibels?
Measured at what distance?
At what rpm are they measured?

What is acceptable sound level?

Graham

"Effective immediately, THSCC will have and enforce a 100 dB sound limit at all of our autocross and rallycross events. For some sites this limit may be reduced to 95 dB, which will be indicated in the event information. All cars are subject to being tested at any place on course, and measurements will be made at approximately 50 feet from the course. Any car which is found to be in excess of the sound limit will not be allowed to start any subsequent runs. This rule is necessary to preserve our relationship with our sites."

100 dB is LOUD people. Only cars that are truly obnoxious and are making people's ears hurt will even be considered for measurement.

This is how the rule is written now. Could change.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Thanks Mike. I just found that it has been added to the Autocross Rules on the thscc website. Maybe a popup would be a nice idea. Since the rules page has changed it would get peoples attention.

I would like to suggest that we make 95db or whatever number across the board. I realize Sanford is more sensetive than Laurinburg for example. But let's just have a consistent number for all sites.

And yes 100db is very loud and also very lenient. Possibly too high.

Graham

DickRasmussen · **Posted:** Wed Dec 15, 2004 8:03 pm

FYI,

I'm not an engine guy, but that rule from Mohawk-Hudson regarding reving an unloaded engine to 1000 rpm below redline for one or two seconds does not "sound" like a good idea for many engines. Hopefully we will avoid having the type of "sound problems with neighbors" that triggered this kind of enforcement requirement!

Michael Westerfield · **Posted:** Wed Dec 15, 2004 9:03 pm

But.... Loud=Good!

Wes Eargle wrote:

Competitors shall rev engine to 1000 rpm below redline for one or two seconds

j/k.... seriously though
Aren't there a lot of newer cars that cannot rev very high in neutral? The RSX, as well as the enterprise sponsered dirtmasters come to mine (oh yes we extensiverly tried reving them in Park). I'm sure there are many more. Guess they'll have to modify that rule.

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

If Enterprise is renting cars that are >100dB then they've got bigger problems than that!

Diane Hall · **Posted:** Thu Dec 16, 2004 10:35 am

Here's our NER sound regs for 2004:

Quote:

Sound Regulations

- All vehicles participating in NER-SCCA Solo events will be required to meet a sound limit of 90dBA measured at 75' at Devens and 94dBA at 50’ at NHIS. This may be measured from any side of the vehicle at any time and includes such noise sources as intake noise and tire squeal. Note that these two sound levels are virtually equivalent. Vehicles which meet one limit should be legal for the other.

- Vehicles such as those in FM and CM which have a GCR-mandated maximum length may exceed that length for the purposes of installing an alternate muffler or exhaust system. The additional length may serve no other purpose.

- After the first violation, the competitor will be required to demonstrate that an effort has been made to reduce sound levels before being allowed to make a second run. This determination will be made by the event chair or a designee. If the second run is still in excess of the allowed sound limit, the competitor will not be allowed to make any additional runs at that event and the competitor will be required to again demonstrate that improvements have been made before being allowed to participate at further events.

- Event staff reserves the right to red-flag a car in excess of sound limits and no re-run will be given.

- These sound regulations will apply at both NHIS and Devens.

We only have 2 sites, and the main one is Devens in Ayer, MA. There was/is a neighbor complaining about the noise there and almost had events limited to "registered street vehicles". (His idea for a better use of the site is a windmill farm. Those don't make noise, do they? :roll:

)

Everyone be really glad THSCC has a bunch of new sites and Miles to manage the process of aquiring new sites. Yay Miles!

Aaron Buckley · **Posted:** Thu Dec 16, 2004 11:04 am

Devens is a decent site, and there really isn't a lot around there but a small town. The townies don't like the autocrossers much either.

I remember running my first Tour there back in 2001. I also remember GH driving Arthur Emerson's Audi TT in GS, and lapping the field so to speak, as well as a monsoon that followed... - AB

DickRasmussen · **Posted:** Thu Dec 16, 2004 1:28 pm

Aaron Buckley wrote:

Devens is a decent site, and there really isn't a lot around there but a small town. The townies don't like the autocrossers much either.

Maybe they think the autocrossers are similar to the crazy GI's (like me) that used to terrorize the roads around Ft. Devens. Lets just say that my brand new 1969 Mustang GT got lots of exercise around Devens and I was one of the most law abiding GI drivers . . .

Mike Winn · **Joined:** Fri Aug 29, 2003 12:30 am **Posts:** 110

Mike is right; 100dB is quite loud and really very generous. If you are louder than that you have a pretty loud car.

I have no idea where I fall, although I do have a decibel meter that I use for calibrating home theater installations (analog > digital for sensitivity.)

Does the club keep a meter in the bus at events? As I drive a car that's not quiet I'd like to know where it comes in at.

MilesBeam · **Joined:** Fri Aug 15, 2003 1:57 pm **Posts:** 427

I'd like to suggest that someone take the initiative and do some research at our first test and tune event in February. If we have to revise something, this would be the time to find out. We can test questionable cars at the launch and perhaps at a point on course where everybody says "mat it" on the course walk.

We all know to our ears what is loud and uncomfortable. We all have some idea what cars are on the borderline. I'd like to see us get some real data to go with our numbers.

Any test engineers in the group want to take that on? I'm the event chair, or I might be willing to do it otherwise.

Miles

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

I've only heard one car that's too loud at our autocrosses, at the June 13th Rockingham event.

I acted as starter at the Viper school, and even though 1 car was fairly loud, it wasn't unbearable by simply turning away after the "whenever you're ready".

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