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[Joe Brugnoni]

I love live sound but also enjoy my redneck side of dirt car racing,,, There is a local track that is in trouble with a local noise ordinance.  long story short it is a unattainable 65 db,, from where they measure I have no idea,,, ANYWAY   Some time ago some engineer told them to place some Semi Trailers around the track to block the sound??They did that and a few other things..The semi trailer are in place on the side of the track closest to town,, They are also in the process of erecting new stands.. They are metal but solid with no Holes in them..

So this is my question as the rumble of motors with mufflers is low pitched,,,is there a way if can measure the primary freq the motors operate at to turn these large boxes (semi Trailers) into some kind of low freq traps?? They could be placed two high if needed,,,  They problem is reduced after the trees have all their leaves and it is hot enough to keep the air on,,  Also with the new stands could they be treat to "absorb" sound if they are not full of people?  I think they are being placed with the idea to divert sound and not that they would be full..

Any ideas,,, thanks,, And if it is a truly dumb question,, sorry in advance!!  Also  Thanks for any advice in advance

[Tom Bourke]

I think it depends on what is harder to change, the laws of physics or the local ordinances.  If the law is poorly written or unenforceable then perhaps a lawyer would do better than an engineer.  In any case try to work WITH the local board and enforcement agency.  Some sort of compromise on time or where the levels are measured.  Get there input and try to show the economic advantages of the racetrack.  Try to form an constructive relationship, not an adversarial one.  You cant fight city hall, well you can try but it gets expensive.

[Jeff Bankston]

ford experimented with a out of phase speaker instead of a muffler and it worked. only problem was the muffler was much much cheaper. record the engines while they are racing. play back at 180deg opposite and see if it works. i am a hot rodder and have a 65 roadrace mustang and go to willowsprings racetrack at times. when i lived in missippi i use to go to 2 of the dirt tracks so i am very familiar with race car exhaust sound and keeping my soda cup covered when the cars pass the stands. the one thing that might make what i suggested not work is the(i forgot the word) and that is as sound is coming toward you , is in front of you and is moving away from you it changes. like a horn on a moving car. its hard to say if barriers will work. at willowsprings when the mustangs,camaros, etc are on the back straight you can barely hear them. when they are on the front straight they are fairly loud. is this race track new ? if the race track has ben in that location for years and the town moved next to them they should be able to get a "go pound sand noise exemption". i live about 1 mile from the airport and love it. the airport was built when all this area was bare land. developers built houses next to the airport and people moved in and for over 50 have ben trying to shut the airport down. the politicians told the people to go pound sand !

[Joe Brugnoni]

ford experimented with a out of phase speaker instead of a muffler and it worked. only problem was the muffler was much much cheaper. record the engines while they are racing. play back at 180deg opposite and see if it works. i am a hot rodder and have a 65 roadrace mustang and go to willowsprings racetrack at times. when i lived in missippi i use to go to 2 of the dirt tracks so i am very familiar with race car exhaust sound and keeping my soda cup covered when the cars pass the stands. the one thing that might make what i suggested not work is the(i forgot the word) and that is as sound is coming toward you , is in front of you and is moving away from you it changes. like a horn on a moving car. its hard to say if barriers will work. at willowsprings when the mustangs,camaros, etc are on the back straight you can barely hear them. when they are on the front straight they are fairly loud. is this race track new ? if the race track has ben in that location for years and the town moved next to them they should be able to get a "go pound sand noise exemption". i live about 1 mile from the airport and love it. the airport was built when all this area was bare land. developers built houses next to the airport and people moved in and for over 50 have ben trying to shut the airport down. the politicians told the people to go pound sand !

The Town was there first,, but the track was built before the the town grew by about 150%  according to the mayor,,,  Lawyers,,, Yes they are looking into the sound issue and the levels that have been set,,, the track is not far from I70 interstate and i would think if I stood in the front yard of a house that the DB levels from the Highway would not change much if any when the track runs,,,   I know that the more "stuff" you have around the more sound will get absorbed,,, so if they could put 6000 fans in there every weekend the bodies would absorb a lot of it... Economics   They track will not generate as much income as property taxes will or will not offset the loss of taxes if property values go down,,,  All of this being said,,, I really was interested if something like this could be done,, most of the other issues talked about have and are being explored

[Joe Brugnoni]

The Town was there first,, but the track was built before the the town grew by about 150%  according to the mayor,,,  Lawyers,,, Yes they are looking into the sound issue and the levels that have been set,,, the track is not far from I70 interstate and i would think if I stood in the front yard of a house that the DB levels from the Highway would not change much if any when the track runs,,,   I know that the more "stuff" you have around the more sound will get absorbed,,, so if they could put 6000 fans in there every weekend the bodies would absorb a lot of it... Economics   They track will not generate as much income as property taxes will or will not offset the loss of taxes if property values go down,,,  All of this being said,,, I really was interested if something like this could be done,, most of the other issues talked about have and are being explored

Maybe its as simple as better mufflers on the cars,,, But I would sure like to know if one of these trailers could be turned into a huge bass trap,,

[Jeff Bankston]

they make race mufflers but they are still loud. as you quiet the exhaust you loose horsepower.

[Steve Alves]

I have heard the technique of playing the noise at 180 degrees to cancel it out but would guess it needs to be exact with virtually no delay. Guessing being this is low frequency it may be pretty expensive to get enough live microphones playing back to subwoofers around the perimeter. But boy that is an experiment I would love to see.

[Jeff Bankston]

I have heard the technique of playing the noise at 180 degrees to cancel it out but would guess it needs to be exact with virtually no delay. Guessing being this is low frequency it may be pretty expensive to get enough live microphones playing back to subwoofers around the perimeter. But boy that is an experiment I would love to see.

the doppler effect is what i was refering to. yes i would probably cost a ton of money and getting it right and dealing with the doppler effect

[frank kayser]

they make race mufflers but they are still loud. as you quiet the exhaust you loose horsepower.

Jeff, you're right on both points.
That said, the track could mandate a spec muffler, same for everyone.  Everyone would lose approx same hp.  Teams could tune around the muffler.

Like it or not, we're losing tracks to noise ordinances.  Racing will eventually have to come to grips with reducing noise.  I'm surprised NASCAR, SCCA, and other sanctioning organizations have not seen the writing on the wall, and taken some steps in noise abatement.  Like the HD folks wanting to hold on to their straight pipes, or Rice Rockets with the race cans.

No, it won't be the same; no feeling the pressure in your chest as a car or bike goes by at full song.  It will better than not racing, however.


Sent from my iPad using Tapatalk HD

[Jim McKeveny]

There aren't easy/cheap/portable solutions. What is needed are "soundwalls", like what you see lining interstates, backed with high-mass earthen berms. Trees are not enough. Sound energy from VLF to VHF reflects up & away (mostly).

Sears Point/Sonoma Raceway enacted this technique first in US years ago with great success. Laguna Seca's location allows this to pretty much occur naturally. Money-tight oval short tracks have a survival issue here. Ditto drag racing.

Then, after you take care of unwanted noise exposure offsite, there are the OSHA regs for onsite support personnel.

BTW- I love racing. I am a huge F1 & Indycar fan since (yikes!) the 1970s. Visceral noise is definitely part of the attraction...But do I want my kids exposed? Not so much.

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