When I use my Spooky2 Central, we are typically about 5 ft away from the tube. It still has quite an effect at this distance.
As for walls, so far I have not seen many issues with the energy having an effect through multiple types of barriers from side experiments I've conducted like how long can I keep bread from molding in ideal conditions for it to mold.
If you can get the tube below your sleeping area within 5 feet of where you will be sleeping, while not as efficacious as having the near field, you should still be well in range for some efficacy.
Much better than forgoing using the plasma altogether.
I'm not sure if sound-deadening materials will help much as the sound is generated by the Spooky2 Central as much as by the tube. Given that you can't block the vents, the sound will make it out of the enclosure probably with little reduction in volume.
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