Sound Absorbing Panels

I have some music projects coming up and since my home studio isn't ready yet, i decided to record the singers in my living room which already sound pretty tight because of the dropped ceiling and the carpet. To make the acoustics of the room even better I made 3 sound absorbing panels of 2x1 meters. I placed them in the corner of my living room and created a nice vocalbooth to record some vocals.

When my home studio is ready in another room I can use these panels in multiple ways. I can place them around a drum kit, create a VO/vocal booth, or just simply use them as sound absorbing panels when recording multiple instruments or singers simultaneously.

Step 1: Be Prepared

I bought my wood at a local guy and he cut it at the right dimensions for me. Most DIY-stores offer this service for free.

- Two scaffold planks of 2 meter
- Two scaffold planks of 1 meter
- One MDF board that fits right in between the planks
- One MDF board that falls right over the outside of the planks

Unfortunately all the MDF boards were 5mm to long so I had to cut them all with a jigsaw.

Step 2: Varnish

I used one layer to make the scaffold planks a little bit more resistant against moisture and temperature changes. The panels will always stay inside so I don't know if this is absolutely necessary.

Step 3: Screw and Glue

I laid the small MDF board on the ground and placed the scaffold planks around it on their sides. I then pre-drilled the holes for the large 7cm screws so the wood wouldn't burst. I did some wood glue in between.
Because the MDF board is in the middle of the planks, the angles of the corners will be close enough to 90 degrees.
When all corners are screwed tightly, it's time for the fabric.

Step 4: Fabric

Remove the smaller MDF board so we can start with the edges for the fabric. I used cardboards shaped in a 90 degree angle, but you can also use normal strips.
Saw or cut the carbon strips to the right size. You don't want to make them too short, because it's handy if the strips stay fixed between the planks when putting tension on the fabric.

Remove the strips, cut the fabric, unfold it and then put the carbon strips back, beginning with the shorter sides.

Step 5: Staple Fun With the Staple Gun

Once the strips are back in place, start pulling on all sides of the fabric evenly until you don't don't have any folds left (except maybe the fold-line in the middle).

Put on staple in the middle of each short side with enough tension and start working around the sides. Start with large steps, a staple every 20 cm or so. And then start stapling in the middle of those. In the end you want to have a staple every 10 cm.

Don't worry if the tension isn't right in one corner. You can always pull out the staple and correct the tension on the fabric.

When you're done, lift the panel to see if the fabric is nicely stapled.

Step 6: Rockwool

Now it's time to put in the rockwool. I used two layers of 4,5cm thick. Each layer has 3 whole panels and a shorter piece you can easily cut with some scissors. Make sure you place the second layer in opposite direction so you don't have the shorter pieces above each other.

Step 7: MDF Board in the Middle

If everything is done correctly, the MDF board will still fit perfectly between the planks without changing the tension on the fabric. First, screw the angle brackets in the MDF board in the middle of each side. The adjust the height of the MDF board to the same amount for each bracket. I choose a dept of 10cm, so the rockwool is tight between the board and the fabric.

Placing the inner board will immediately stabilize the panel and making it solid as a rock(wool).

Step 8: MDF Board on the Back

By putting a second MDF board on the back of the panel, I've created a gap of stationary air and traveling sound really doesn't like that. Because of a miscalculation of my local wood seller I had to shorten the boards with 5mm, but with some wood clamps and a jigsaw that's not that big of a deal. (It's nice to have family with a lot of equipment ;) )

Step 9: Last Important Step

To keep this large, heavy panel from falling, I placed 4 larger angle brackets on each corner. You can also screw some larger planks below the panel but I preferred these connections. Make sure the screws that are the lowest to the ground, don't clash with the other ones already in place. But don't used screws that are too short, you don't want to see your dog get squashed!

A handle on the opposite side helps to move the panel with help from someone else. I'm gonna place skateboard wheels in the future so I can easily move it on my own.

Step 10: ​So What Stuff Do You Need?

- 4 scaffold planks (2x 100cm, 2x 200cm)
- 2 MDF boards (depending on the thickness of your planks, 1 MDF board of 95x200cm, 1 MDF board of 100x205cm)
- 12 long screws, 3 for each corner (wood glue is optional)
- Fabric. The density of the fabric can't be too high, sound must be able to get through it.
- Cardboard strips
- Staples
- Rockwool, 6,6 pieces of 100x60x4,5cm)
- Smaller screws (for the brackets and the backside MDF board.
- Small angle brackets, to secure the smaller MDF board.
- Stronger screws for the larger brackets to keep the panel from falling. (You can also use wood planks or what you like)
- Strong handles and/or some small wheels to move the panels easily.

Handy equipment:

- Drilling machine
- small drills
- Jigsaw
- Wood clamps
- Normal handsaw,
- Scissors
- Staple gun and staples
- Machinist square
- Flatiron

Step 11: End Result

I'll post some more photo's of the end result soon and maybe also some sound samples!

Let me know what you think!

Comments

[Florios]

I'm really confused as to why you put the MDF board in there. I've done tons of research on this subject but am by no means a pro. but from my understanding the air gap is supposed to be between the insulation and a wall. Not MDF board and a wall. This should in theory catch SOME high end and pretty close to no low end at all.

[Florios]

and to add to that if it's just in the middle of the room is best not add MDF cause instead it of letting waves go further away it will reflect.

[Bricology]

It's my understanding of acoustics that you're correct on all points, although I'm not an expert, but I have built an isolation booth for recording, which functions as intended.

At the risk of saying things you probably already know -- there are a number of reasons for building panels like this, but they would be very unlikely to affect sound *transmission* to any appreciable degree. The point of an air gap is to isolate the interior plane from the exterior one. But to do so effectively, the air gap should be between materials that are *dense* and *immovable*. That's why isolation booths are typically made of very heavy materials (like masonry) or multiple layers of thinner, lighter materials (like the 3/4" plywood, 1/2" drywall, 1/2" MDF glued-and-screwed sandwich that the exterior walls of my booth are made from).

If the exterior walls are thin enough to be affected by soundwaves, they will transmit those waves to the inner walls, which will sympathetically resonate. So two sheets of thin MDF in parallel with an air gap between them will just function as a transducer -- like a giant drum.

The point of acoustical treatment panels, OTOH, is usually twofold: to prevent soundwaves from reflecting back to the workspace, and to absorb certain, undesirable frequencies. To prevent reflection, the materials have to effectively absorb *all* of the sound frequencies that are produced. And to capture unwanted frequencies, the material's density and thickness have to be tailored to those frequencies. In general, the lower the frequencies to be absorbed, the thicker and denser it needs to be, and the density should progressively *increase*, to absorb a range of frequencies. Panels like the ones in this Instructable, would only absorb those frequencies that tend to be captured by the density of the rockwool he used, which might only be say, 300-350hz; everything else would be unaffected.

I built sound traps into my booth that are intended to absorb everything below 400hz (which isn't completely achievable). They're made of three different densities of materials: 2" thick convoluted acoustical foam, 4" thick, kraft/foil-faced spun fiberglass insulation, and 2" thick dense fiberglass panels (O-C 705), and all of this mounted onto 3/8" perfboard panels whose holes allow soundwaves to escape to the area behind and get trapped in an air-gap. It's far from professional, but it does seriously reduce *all* soundwave reflection and in particular, the reflection of low-frequency sounds.

[GabeH4]

How much did this cost to build? i built sound dampening panels using 2x2's and foam. Thinking about designing something like this and seeing if i can build myself something more sophisticated lol.

[Kimtrumbore]

I have never seen those cardboard strips. Please explain where I could find them.

[PeterP_DIY]

They're called pallet corner protectors. Greenhouses, for example, use them to protect the products they're shipping.

[shambuda2000]

It would be very interesting to see a decibel reduction number.

[darrenbassett]

Fairly straight forward and basic, but not an instructable by any means. What of those with poor woodworking skills?

[PeterP_DIY]

It's updated now!

[darrenbassett]

Thank you, as I say, others in the community would need the extra advice and input you have provided. Not all on here are as technically or practically skilled. Good instructable.

[LairdDeimos]

Wait, did I miss the insructable?

[PeterP_DIY]

Working on it as we speak!