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Soundproof a Rock Tumbler: Quick Fixes For 75% Less Noise!

Rock tumblers are amazingly simple yet effective machines, but one of the most common complaints their users have is the amount of noise they produce. It’s a shame when would-be rock tumbling enthusiasts have to abandon the hobby because their rock tumblers are too loud for themselves, their family, or even their neighbors to listen to around the clock. I’ve found several surprisingly effective ways to limit the noise coming from my rock tumbler so I wanted to share them with you.

To reduce the noise from a rock tumbler, use a rubber tumbling barrel, soft tumbling media, and perform any necessary maintenance on the motor. To further muffle the sound, surround the tumbler with a noise-reducing baffle box, place it on a towel, or move it to an unused space in your home.

I have tried most of these methods myself with some degree of success, but which solution works best for you will depend on your tumbler type, living situation, and budget. I’ll dive deeper into the effectiveness of each of these techniques so you know exactly what to expect.

Methods for Quieting a Rock Tumbler

Noise from a rock tumbler comes from two places: the tumbler motor and, more notably, the tumbling rocks impacting the sides of the barrel. Some of the fixes below address one or the other of these sound sources, but most will help with both. When using your rock tumbler make sure to follow the manufacturer’s instructions and guidelines.

I will reference decibels (dB) frequently in this article, so keep in mind that it’s a relative scale. A difference of +10 dB is roughly equivalent to twice the noise level. So, 60 dB will sound about twice as loud as 50 dB to the listener. Below is a chart just for a frame of reference.

Environmental NoisedBA
Jet Engine (100′)140
Chain Saw (3′)110
City Traffic85
Vacuum Cleaner75
Normal Conversation65
Decibel Chart (Source)

Use a Rubber Tumbling Barrel

Depending on the type of rock tumbler you have, the biggest culprit when it comes to obnoxious noise may be the material your tumbling barrel is made from. Cheap, toy-style tumblers that are normally marketed towards children usually have hard plastic tumbling barrels. In contrast, quality entry-level tumblers like this one I recommend from Amazon come equipped with rubber barrels that significantly reduce the noise generated by the moving rocks inside. You can hear the difference demonstrated in this video:

A nice rubber barrel is one of the reasons I highly recommend the National Geographic Professional 3 lb. Rock Tumbler. The noise reduction and quality of the polish it produces are well worth the incremental cost over a cheaper beginner’s rock tumbler.

If you have a tumbler with a plastic barrel you may not need to invest in a completely different tumbler to mitigate the noise. You can buy extra barrels like this one on Amazon made of quality rubber. You’ll want to check the widths of your tumbler and your replacement barrel before ordering to make sure the barrel will fit.

Build a Sound Dampening Baffle Box

This is my favorite solution in this entire list because it works no matter what type of tumbler you have or what the source of the noise is. You should watch my video below of the build process, but the basic idea is fairly simple.

You create two boxes – the first of which is just large enough to completely cover your rock tumbler, and the second of which is a couple of inches larger in each dimension. Then you stack the larger box on top of the smaller one and fill the void space with fiberglass insulation. I managed to build one in less than an hour and it reduced the noise from my rock tumbler by 50%!

The only new material I had to buy for this build was the roll of fiberglass insulation. You can buy the exact stuff I used on Amazon but it would probably be cheaper at your local hardware store. For the smaller box, I used the box my tumbler came in, and I happened to have a bigger box that was almost the perfect size to match. You can get creative and make your own boxes with the appropriate dimensions with big leftover cardboard boxes and some duct tape.

One of the common objections to this fix is that it will overheat your tumbler’s motor. However, I did a temperature check on the motor of my tumbler before and after running it for an hour with an unventilated box and the temperature was only 3° F more than without the box. The next day I ran another test after cutting a ventilation hole near the motor and found absolutely no difference in temperature.

Put a Towel Underneath the Tumbler

This is one that I hadn’t yet tried until I decided to write this article but I commonly see being recommended. The intention of the towel is to reduce vibrations (and therefore noise) sent into the floor. When I tested this for myself with my decibel meter I only picked up a few decibels difference at most. I have LVT flooring, so this method might very well work better with hardwood floors or if the tumbler is commonly kept on a shelf where it is more likely to vibrate.

Place Tumbler in an Unused Space

This is the solution that I normally use, and is by far the most common solution for most rock tumbling hobbyists. The vast majority of rock tumblers are kept in a garage, shed, or basement just to separate them from the family’s living space. Unfortunately, this often isn’t an option for many people who live in apartments or other tight quarters. Garages and sheds may also become too hot or cold to run the tumbler.

But not to fear, there still might be a solution here for you! If you can make room in a cabinet in your kitchen or on the floor in a closet that will go a long way in mitigating the noise.

There is usually a lot of ambient noise in the kitchen from appliances, so adding the rock tumbler into the mix might not be as big of a deal in that space. See if you can put it into a large cabinet and combine that with some of the other techniques I’ve discussed. I myself usually keep my tumbler on the floor of my gym closet, and with the door closed, we can’t hear the tumbler at all from the adjacent family room. Just closing the closet door reduces the noise level by 9 dB (almost 50%).

Use Appropriate Tumbling Media

Regardless of the type of tumbler you have, another strategy you can employ to reduce the noise from the barrel is to use tumbling media. One of the purposes of tumbling media is to cushion the impact of rocks in the tumbler and help smooth the ride. The primary goal is to mitigate any unwanted damage to the rocks, but a side benefit is reducing the amount of noise caused by the rocks being flung around inside the barrel.

Tip: Check out my article on the types and uses of tumbling media

If your only objective is to reduce the amount of noise generated by the rocks then I would highly recommend Polly Plastic’s plastic pellet tumbling media from Amazon. Plastic pellets are specifically designed to cushion rocks in the barrel and will likely be the quietest option. That being said, I would still recommend Polly Plastic’s ceramic tumbling media for general use. It will help reduce noise while also producing the best results.

Perform Routine Maintenance

A less common (but no-less annoying) source of excessive rock tumbler noise is the motor. Rock tumblers are designed to be continuously operated for weeks and months on end, and while quality tumblers can go for very long periods of time with little to no maintenance they do occasionally need to be serviced.

You’ll want to consult your tumbler’s manual for a servicing schedule and make sure that the motor is in tip-top shape. This may include oiling some moving parts or replacing things on the tumbler such as the rubber belt, bearings, or shafts.

Combine Solutions For Best Results

In order to get the very best results, I suggest you try combining a few of these techniques. By putting my tumbler behind a closet door and covering it with my homemade baffle box I managed to reduce the noise by 15 dB – a whopping 75%! Experiment with your setup and you should be able to get similar results. Hopefully, you and your family can continue to enjoy this hobby without the constant noise driving everyone insane.