Does Sand Absorb Sound?
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While soundproofing my outdoor seating area, I looked for effective natural products to use. This got me wondering, does sand absorb sound? If you’ve wondered the same, here’s a quick answer:
Sand absorbs sound very well. This is because it’s relatively heavy and made up of very small particles. Grains of sand fit together very tightly, which blocks both airborne and impact noises from passing through. In fact, sand can absorb a much greater portion of sound than soil.
Also read: Does a Brick Wall Absorb Sound?
In this article, I’ll go into a bit more detail about how well sand absorbs sound, and what you can actually do with this information.
How Well Does Sand Absorb Sound
You might not have considered it before, but sand is quite an interesting material. It’s made from tiny grains of rock that are broken down over a very long period of time.
This makes it surprisingly effective in the world of soundproofing. For effective noise blocking, we often rely on core principles. These include:
- Mass. The more massive the material, the better it absorbs and blocks sound.
- Dampening. A material that dampens essentially doesn’t vibrate when in contact with sound waves.
Sand has both of these properties. The tiny individual grains of sand provide it with plenty of mass in a relatively small space.
What’s more, they can fit together very tightly, leaving almost no room for air in between. This is very useful for absorbing and reflecting sound.
Also, grains of sand do vibrate, but vibrations don’t pass through sand effectively. Sound vibrations lose energy when they make particles vibrate, and so the sheer number and density of particles in sand mean they lose energy quite quickly.
The sound absorption properties of sand have actually been studied. Dense sand was found to have an attenuation coefficient of 25dB. In simple terms, this is quite a lot.
It’s also been proven that you can increase this value by making the sound wet. This is hardly a surprise because saturating the sand both increases its mass and allows the grains to make together more tightly.
Wet sand was found to be even more effective at higher pitches, which is another bonus for soundproofing.
Yet another study found that employing the non-Newtonian properties of sand can be very effective in soundproofing.
A non-Newtonian fluid is one that has the properties of both a liquid and solid. When force is applied, the liquid compacts and becomes, in effect, a solid. With enough force, you can even walk on it.
Quicksand is basically a non-Newtonian fluid version of sand. For more information, I recommend you check out this video on non-Newtonian fluids.
In short, we can conclude that sand has the potential to be quite an effective soundproofing material. It has all the properties we need for sound absorption and dampening in a wide variety of states.
How to Use Sand for Soundproofing
However, what holds us back is what we can actually do with this information. After all, you can’t exactly line a room with sand and hope it’s suddenly soundproof.
Here are my top suggestions for how you can use sand for soundproofing around the home.
1. Insulate floors
As I mentioned, one useful property of sand is that it’s heavy. But this also realistically limits how you can use it about the home.
One suitable option is to insulate the floor cavity of your ground floor living spaces.
This will reduce the amount of sound transfer into the structure, as it’ll prevent it from passing from the floor into the support joists.
Obviously, this’ll require pulling up floorboards and buying lots of sand, but filling the floor cavity will do a good job.
I wouldn’t recommend insulating upstairs floors with sand because over time it’ll just turn the downstairs into a giant egg timer.
Sand has an amazing ability to find even the tiniest gaps, much like liquid. One small crack and your house will be flooded with escaping sand. Not good.
To do a good job of the downstairs floors, you’ll probably need 3-4” of sand, or more if you have the space.
2. Build a room in a room
If you’ve been researching soundproofing solutions, you’ll probably already know that decoupling is one of the best methods.
You can do this by building a room within a room.
Sand can be a useful addition for this kind of project, particularly if you’re looking to save money.
You can use sand as wall insulation instead of something like mineral wool. Granted, it’s not that expensive, but perhaps you don’t have the budget for it.
Build walls out of thick plywood or MDF. MDF is better because it absorbs more vibrations than plywood.
You’ll need to mount these on a frame and seal with something like weather stripping (Amazon link).
Leave a 4” gap between the 2 sides of the wall and fill the cavity with sand. This is an excellent (and inexpensive) way of adding plenty of mass to your walls.
3. Insulate a door
The vast majority of interior doors are hollow, which obviously isn’t great for sound transmission. Doors are always an area of weakness when soundproofing a room, and finding effective solutions is difficult.
Sand could offer an option for reducing sound transmission through a door. Essentially you’ll fill the door’s core with sand to greatly improve its mass.
Here’s my suggested method:
- Cut the top off the door to expose its hollow core (you could alternatively drill a series of small holes).
- Check the door for any holes or cracks and fill with Green Glue.
- Fill the interior with sand, but ensure it’s completely dry.
- You could bake it in the oven for an hour or two first.
- Fill the holes with Green Glue or glue the top back on.
- Hang the door on heavy-duty door hinges designed to take the extra weight.
I recommend being careful about the door you use, though. It’ll need to be a higher-end model with superior construction.
Cheaper doors could crack or buckle under the extra weight, which will result in a big mess in your home.
Alternatively, contact a local woodworker or shop for more assistance, as this could become an in-depth project.
4. Use it outdoors
Sand is perhaps most useful outdoors because it could prove messy indoors. You could always try using it in novel ways for reducing sounds around an outdoor space, such as a seating area.
I suggest containing it in boxes of some kind. For example, you could build custom designs from Perspex or a similar material. You could then use these as sound barriers.
Another option would be to insulate a fence with sand as I suggested above. You could build a fence from mass loaded vinyl (Amazon link) or similar vinyl material and then fill the inner cavity with sand.
Some Final Thoughts
Sand has the potential to be useful when it comes to absorbing sound. But it’s really not the most practical material to work with, mainly because of its liquid-like properties.
I’d recommend sticking with more conventional soundproofing products. They might be pricier, but at least they won’t turn your house into a sand castle.
