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Helmholtz resonators (be forewarned, this is a fairly random question, tweak for road music..)

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Not looking for a home helmholtz setup. Actually looking for more discussion about the hows and whys they work, and if I could apply it to a car.

What I am looking to do is reduce a specific frequency sound. Many people will refer to the sound I am talking about as "droning." My thinking is because of the piston in the car acting similar to a woofer, the exhaust pipe becomes like a port in an enclosure and is "tuned" to a specific frequency. Unfortunately it produces a rather loud sound at that frequency. The choices are to either change the resonant frequency by length or width of the pipes, or reduce the amount of sound the pipe produces at that frequency. (of course reducing the total sound is also a possibility, but I would rather have the rest of the sound this particular exhaust produces. its my type of road music :D!)

Most of the time they are just small unfilled chambers welded onto a central pipe and covered by the muffler shell in a normal car. Unfortunately the formulas used to come up with those chambers are not publicly available AFAIK. Figured if anyone knew anything about it, this would be the place to find them!


I think the resonance is in the 200-300hz range, but have not gone and figured out the specifics yet. Want to see if its possible at all first. SPLs in the 105-110 db in car range while droning. (hence the issue)


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Topic - Helmholtz resonators (be forewarned, this is a fairly random question, tweak for road music..) - Scot Kight 15:47:10 06/17/02 (6)


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