Soundproofing Box Project

     Although the tumbler isn't TERRIBLY loud... it was still a nuisance at times. Especially towards the tail end of the week, when the rocks have shrunk a little and it gets a little louder. The first thing I tried was just to put it in a cardboard box with some old 1/8th inch vinyl (it can help absorb sound) that was lying around. It was noticeably quieter, but not quiet enough. That is without even mentioning the motor housing was almost too hot to touch, after just an hour! 

    Not wanting to fry the motor on my new brand tumbler, I began brainstorming ways to keep it quiet without sacrificing airflow. The natural course of thinking is "How about I put some holes in a box for a fan to blow air?" However, that leads to an obvious flaw... a hole means a great big place for sound to travel. Rather than scrap the idea of a fan to circulate fresh air, I had to think about how sound is mitigated in other systems that have airflow. The first two parallels I drew were to car mufflers and firearm suppressors. While these are not exactly the same when you really dig in, there was a core concept to exploit. Surface area, distance sound waves have to travel, and any obstacles those waves meet.

    Essentially, if you make a channel the air must flow through, and it has obstacles redirecting it (e.g. turns with no straight path outside), then the soundwaves will have a hard time reaching the end. This was enough for me to visualize the design I wanted over a day or two... but you can't really measure things that you imagine. So I downloaded FreeCAD, watched some videos on how to use it, and got to work! After several hours of fumbling around, and a few more iterating on the design, I'd modeled something I was happy with.

    I based the size off of measurements I had taken of the tumbler, and the wood I had on hand (4' x 6' x 3/4" pine plywood). I wrote down the dimensions of each piece I would need to cut and got to working. Thankfully I already had most of the tooling and materials I would need before starting.

Scribed out every piece I needed, although I didn't account for losses from blade thickness when cutting

The pieces were cut out, though without a table saw. I used a circular saw for most of the cuts, and a few finished by a miter saw. As a result of not measuring for cutting losses, and lack of practice in cutting, they were a little misshapen but not enough to cause major issues.

1-1/2" wood screws were used to fasten everything together, but there was noticeable gaps between some of the boards. This issue was solved by just caulking any gaps in the main box, and in the first chamber of the exhaust/intake.

    After caulking, a layer of vinyl was added to the main chamber to help absorb as much sound as possible, just glued down. Two cheap computer fans with a USB cord for wall adapters were installed where the holes in the main chamber are. Along with a few other finishing touches, like a notch for the cables to be run, and eye hooks to allow a bungee cord to hold the lid down. Six rubber feet were also added to isolate the wood from whatever it would be placed on, more noise isolation!

    The final product looks a little shoddy, but it works like a charm! The sound is significantly quieter, and the motor even stays cooler than when it was running in open air. The inside is cleaned every week to keep dust down, alongside the normal tumbler maintenance of oiling the bearings. For a sense of scale the footprint is 21.5" wide, 18" deep and about 10" tall in the middle.

    I have another project on the horizon though I want to take my time with it, as it will be indoors and in plain view. Nothing crazy, just a box for storing (and loosely sorting) rocks that I have collected that will end up in the tumbler. I don't expect to build anything to use as a display as my craftsmanship is not nearly nice enough for that.

This post may be a tad longer than necessary but hopefully some of you find it interesting!