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[Simon Lewis]

Active noise cancellation is not going to work in this situation. To reduce noise levels at the sensitive properties, you woudl need to reduce noise at source or provide effective barriers. By "effective" I would suggest a large earth bund. Here's an example that was used to protect a nearby town from jet engine test noise:

http://maps.google.co.uk/maps?q=hucknall&hl=en&ll=53.017681,-1.221886&spn=0.004434,0.011362&sll=52.8382,-2.327815&sspn=9.123282,23.269043&hnear=Hucknall,+Nottinghamshire,+United+Kingdom&t=h&z=17

 

[John Roberts {JR}]

It would have to be a live microphone. If you can duplicate the sound exactly 180 degrees out of phase, it would cancel out. (Theoretically but probably not possible)

shhhhush..

Actually they have made vehicle mufflers that work using active noise canceling, but in that case they have good information about and good control over the specific waveforms they wish to cancel.

In 3d space, with multiple moving noise sources not remotely practical.  Too expensive to apply to each vehicle... think dirt, lots of dirt.

JR

[Art Welter]

Quote from: Doug Fowler  at 02:55:33 pm

    "180 degrees" at what frequency?

It would have to be a live microphone. If you can duplicate the sound exactly 180 degrees out of phase, it would cancel out. (Theoretically but probably not possible)

The cancellation would occur at only one place in space.
In other areas, the additional "noise cancelling" sound would create areas of additional SPL.

To use "noise cancelling" sound would require a loudspeaker/mic/amp at the location of every person that complains about the noise, totally impractical.

A sealed wall of trucks,  a sound wall as used along hiways, a dirt burm, or mufflers on the cars all would work without huge expense.

[Brian Jojade]

Quote from: Doug Fowler  at 02:55:33 pm

    "180 degrees" at what frequency?The cancellation would occur at only one place in space.
In other areas, the additional "noise cancelling" sound would create areas of additional SPL.

To use "noise cancelling" sound would require a loudspeaker/mic/amp at the location of every person that complains about the noise, totally impractical.

A sealed wall of trucks,  a sound wall as used along hiways, a dirt burm, or mufflers on the cars all would work without huge expense.

For noise canceling to work, you'd either need headphones on each individual, or have the noise canceling happen as near as possible to the source.  The inverse square law from point of origin would mean that if you placed the canceling sound at a significant distance from the source, the levels would offset only at one single point.  So, sound canceling on each vehicle at the exhaust point could be possible, at least enough to be partially effective.  Cost and implementation likely quite prohibitive, as your sound canceling device would need to be able to create the SPLs that the engine does at the exhaust point.  Good luck with that.

Solid dirt walls will work the best.  Semi trailers are a partial solution, but won't block all frequencies.  They'll help, but may not do as much as needed.

Knowing the exact rules is key to this game.  Realizing the exact rules don't exist means you have to play politics more than anything else.  65dB is all you mentioned for the max volume, but not knowing WHERE that measurement is makes it much more difficult to achieve.  6000 people in the stands will create more noise than that, by far.  Now, if you get them to pinpoint a location that it has to be 65dB, you can set up your sound barriers so that you fit within the rule.  However, if the sound is still annoying to residents, then the rules WILL change, and your efforts are lost.  For some people, just being able to discern the sound of the racetrack will be too much.  You won't be able to measure any increase in volume with a dB meter over ambient noises, but it's still going to irk someone.  If you find a way to make them happy, that's cheaper than eliminating the sound completely.

[Patrick Tracy]

Knowing the exact rules is key to this game.  Realizing the exact rules don't exist means you have to play politics more than anything else.  65dB is all you mentioned for the max volume, but not knowing WHERE that measurement is makes it much more difficult to achieve.  6000 people in the stands will create more noise than that, by far.

You also need to know the weighting (A, C) and time range (peak, fast, slow, continuous equivalent) that's specified.

Now, if you get them to pinpoint a location that it has to be 65dB, you can set up your sound barriers so that you fit within the rule.  However, if the sound is still annoying to residents, then the rules WILL change, and your efforts are lost.  For some people, just being able to discern the sound of the racetrack will be too much.  You won't be able to measure any increase in volume with a dB meter over ambient noises, but it's still going to irk someone.  If you find a way to make them happy, that's cheaper than eliminating the sound completely.

Ultimately it will come down to psychology. The street outside their door may be objectively louder than your noise at their location, but if they just don't like hearing race cars then any audible level will be considered objectionable. If they don't like the music it's too loud no matter what. If they like the music it's never loud enough.

[Joe Brugnoni]

You also need to know the weighting (A, C) and time range (peak, fast, slow, continuous equivalent) that's specified.

Ultimately it will come down to psychology. The street outside their door may be objectively louder than your noise at their location, but if they just don't like hearing race cars then any audible level will be considered objectionable. If they don't like the music it's too loud no matter what. If they like the music it's never loud enough.

Thanks so much for all the replies!!

Yes,, it seems that the best solution is better mufflers and the owner shot himself if the foot a couple years back when he opened the rules to get more cars quickly, And you know we racers NEVER Cheat!! LOL  So while I do not think that there is one solution,, it seems that combining a few things might effect some changes,, reflecting the noise is possible..

Big earth berms,, not so much,,, if the track did not sit on top of an old marsh,, maybe they could have just move it deeper into the ground this winter,,,,

The trailers do set on their wheels at this time and are not tightly stacked or pushed together

Basically the track sits in an east west alignment with the city to the west of the track,,, had it been possible to build the track in a north south way and place all the stands and scoring towers on the west side it may have helped..

They have a Sprint Car show tonight,,5/22,, I am going and for fun taking my DB meter,,, gonna play with that a bit both a and C weighted and see what happens.. Thanks again for all the replies,,, 


I think that a call to some of the suppliers of headers and mufflers for these cars is in order,,, I will bet there is a way to make them sound like a street car and still keep a lot  of the power. 

 

[Jerome Malsack]

Earth burms may eventually sink in.  but if you build the skirts onto the trailers to create a solid wall then add some earth burms inside the trailers.  Keep the earth burms inside the trailer as 1 foot wide floor to ceiling and filled.  This will allow the trailer to act like a ship and float and distribute the weight to keep it from sinking.  Providing a double chamber internal to allow some tuning if needed.  Place the one on the bottom on the roof upside down and the wheels in opposites Giving one hole between the trailers to cover and one area to fill a burm in the middle.

[Cosmo]

As Patrick noted, you need to see exactly what the law states as far as which scale this is measured with.  You might be able to beat them at their own game.

If they are using A-weighting, the low frequencies fall off rather quickly on that scale, and you MIGHT be able to affect the measurements with the treatment you described, since you would be cutting into the middle frequencies.

If they are using C-weighting (or especially Z-weighting) then you are pretty much SOL.

Of course, this all goes out the window if there is a temperature inversion at the wrong time and all the noise goes over the barricades.

[[email protected]]

Earth burms may eventually sink in.  but if you build the skirts onto the trailers to create a solid wall then add some earth burms inside the trailers.  Keep the earth burms inside the trailer as 1 foot wide floor to ceiling and filled.  This will allow the trailer to act like a ship and float and distribute the weight to keep it from sinking.  Providing a double chamber internal to allow some tuning if needed.  Place the one on the bottom on the roof upside down and the wheels in opposites Giving one hole between the trailers to cover and one area to fill a burm in the middle.

Giant earth deflectos are the only real solution to a problem like this. After implementing those neighbors will likely continue to be annoyed by the unwelcome noise pollution regardless of the levels and you may need even bigger piles. Once the berms are established... you may consider localized inverted signal cancellations. But this would need to be implemented with measurement mics and delayed output to coincide with the arrival time at each speaker. Anything short of (I would think at least at every 30 degrees of horizontal noise spread on the far side of the berm perimeter) this will likely be fruitless efforts.

If it were my design I might also consider some extraneous noise output to decrease the ratio of 'car engine' to 'other sound' also originating outside the berm perimeter. Home owners are much more tolerant of bird song, or "white noise wind" for instance. And if this were 30db louder than the race track, that might be a good step in the right direction.

[[email protected]]

For your metering pleasure... Many city ordinances specify the DB limit levels to be at property lines (pick the shortest line to a neighbor).

[ProSoundWeb Community]