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this is my first post here! I wanted to share my ideas for this and get some input on them.

My parents were kind enough to let me put a cnc machine in the loft. (shapeoko 3 xxl) In order to make them not regret their decision, I need to go to some extreme measures for sound deadening which are

  1. Dual Pane extruded acrylic windows with a helium filled 3/4" gap in-between.
  2. Active Noise Cancellation.

Helium, in as little as an 8mm gap, can provide tremendous sound dampening properties! up to 20db of suppression. the windows will be sealed with a nitrile adhesive as nitrile has a low permeability to helium. search "tech ingredients helium vs sound" on youtube to see demonstrations on helium's incredible sound suppression properties! you can also check out his active noise canceling demonstration too.

Active Noise Cancellation I will place electret-type mics on each wall of the enclosure with a piece of soft foam in-between the mic and the wall to decouple the microphone from the surface transducer which will be mounted on the outside of the enclosure on each wall. the microphone signal gets sent to an amp, which then drives the transducer which makes the wall vibrate. we then wire it so the signal is out of phase thus canceling the vibrations. I already ordered two transducers and a two channel 50w amp (cheap class d one from amazon) and will begin testing this weekend.

Basically I need some input on the design as well as a few questions answered.

  1. will the fact that the cnc machine is moving around the enclosure (the source of the sound is constantly shifting) cause any issues with the overall performance?

  2. will the helium leak out at an inconvenient rate? there will be two valves on the top and bottom of each window for helium filling and re-charging. all I need to do is use helium filled balloons as my helium source. Not sure about the permeability of extruded acrylic is to helium. the nitrile glue is supposed to be one of the best gasketing materials for helium as it isn't very permeable to helium. im hoping ill only have to "recharge" the windows every few months.

any general input and ideas would be much appreciate!

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    $\begingroup$ Isn't the main problem conducted noise thru the body of the machine to the structure of the house? $\endgroup$
    – D Duck
    Apr 8 at 22:29
  • $\begingroup$ The machine will be on a soft rubber mat and the table top it’s sitting on is dampened with a layer of silicone adhesive in between the table top and the frame. $\endgroup$ Apr 8 at 22:47
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    $\begingroup$ I'm a bit skeptical that you can cancel all modes of wall vibration across such large areas. Better just to put up sheetrock with eggcrate foam or even rolls of fiberglass insulation attached. Absorption is easier to achieve than cancellation $\endgroup$ Apr 9 at 12:04
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    $\begingroup$ I’m voting to close this question because good (and workable) answers are more likely to be found at diy.stackexchange.com $\endgroup$ Apr 9 at 12:05

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