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Thread: Engine noise abatement

  1. #106
    Join Date
    May 2016
    Location
    Dorset UK
    Posts
    91

    Default Re: Engine noise abatement

    Something you might want to investigate is intake noise, its far worse on diesels due to there being no throttles.

    There is also something called https://en.wikipedia.org/wiki/Helmholtz_resonance, if you look at any modern car intake & even exhausts you will find a blanked off box or tube built in. It matches the volume of the intake resonance at certain RPM's. Remarkably simple to make & test with a y peice & variable length of tube. As these engines really only have a small rev range it will be easy to find the sweet spot.

    This is what its all about, find the resonance noise spot & kill it with a Helmholtz resonator - simples

    The theory of Helmholtz resonators is used in motorcycle and car exhausts to alter the sound of the exhaust note and for differences in power delivery by adding chambers to the exhaust. Exhaust resonators are also used to reduce potentially loud and obnoxious engine noise where the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.

  2. #107
    Join Date
    Oct 2018
    Location
    lagunitas, ca, usa
    Posts
    490

    Default Re: Engine noise abatement

    Okay, finished with engines .... I have a box around about half the engine and had most of a mat left over, so did that today. It made more of an improvement than I expected .... probaly not enough for Snoose but at least another increment better here. It's now louder outside than in, good enough for me.

    I think, Mr Snoose, that if you want Lexus-level peace and quiet you'll have to remount the engine on soft mounts thru the roll center and all that. Otherwise they just shake the whole wood structure and you're never going to damp all of that.

    But burying the clatter under blankets made it tolerable for me.

    One other thing to mention about stable mats - a rasp works nicely to fine-tune the edges if your jigsaw wasn't perfectly straight. I try to make the fit a touch too tight, then place the edges where I want and sqush the middle down last. They compress a tad and that makes the fit nicer ... but hard to trim off a 1/4" in rubber, a rasp does that very well. A Surform might work, too.

    Too bad you don't get good at something until you are alnost done

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