acoustic isolation pad material for DIY

[pjd3]

Hello, thanks for stopping by.

I finally have a decent home recording solution for recording my new acoustic guitar as far as mics, cables, AD conversion, FX and DAW are concerned.
Still however, there is the issue of having to record in small square rooms with hard parallel walls which means heavy standing waves, hard flutter echos.
After watching some DIY foam and box projects I'm hoping for something a bit better than the 1 inch foam inside a 12" x 12" box. While I do hear a reduction in room echo it is still there quite a bit and I detect the presence of a "box", an emphasis on certain frequencies that don't seem to be there outside the box - I take that as there are some light standing waves developing inside the box due to some acoustic transparency still occurring with the 1 inch foam and reflections from parallel walls inside the 12" x 12" box. That doesn't surprise me, I'd expect some of that.

As an improvement on that, I imagined for one, that using something like a trapezoidal shaped bucket of sorts may be better than a square box as there would be far less tendency for sound waves to build up upon each other (reflections would be likely to quickly exit the bucket due to the back of the bucket being much smaller in diameter than the front where the mic would face out). Coupling that with an acoustical isolation material that absorbs mids and high frequencies better than the typical cheap 1 inch foam seems like it would present a far better removal of bad room acoustics than the square box with just one inch foam.
I've noticed other materials out there, such as "Echo Absorber Panel" from Soundproof Cow. Of course, I have no direct experience with these solutions so, I was hoping some of you might chime in with DIY solutions that you found to be superior to other materials and solutions.
Unfortunately, I was like a greedy little kid for my Christmas list and Santa has an eye on me at least for a little while till we catch up so, gatta keep it affordable - thus, DIY!
Thank you all, looking forward to your feedback
Phil Donovan

[TBman]

Originally Posted by pjd3

Hello, thanks for stopping by.

I finally have a decent home recording solution for recording my new acoustic guitar as far as mics, cables, AD conversion, FX and DAW are concerned.
Still however, there is the issue of having to record in small square rooms with hard parallel walls which means heavy standing waves, hard flutter echos.
After watching some DIY foam and box projects I'm hoping for something a bit better than the 1 inch foam inside a 12" x 12" box. While I do hear a reduction in room echo it is still there quite a bit and I detect the presence of a "box", an emphasis on certain frequencies that don't seem to be there outside the box - I take that as there are some light standing waves developing inside the box due to some acoustic transparency still occurring with the 1 inch foam and reflections from parallel walls inside the 12" x 12" box. That doesn't surprise me, I'd expect some of that.

As an improvement on that, I imagined for one, that using something like a trapezoidal shaped bucket of sorts may be better than a square box as there would be far less tendency for sound waves to build up upon each other (reflections would be likely to quickly exit the bucket due to the back of the bucket being much smaller in diameter than the front where the mic would face out). Coupling that with an acoustical isolation material that absorbs mids and high frequencies better than the typical cheap 1 inch foam seems like it would present a far better removal of bad room acoustics than the square box with just one inch foam.
I've noticed other materials out there, such as "Echo Absorber Panel" from Soundproof Cow. Of course, I have no direct experience with these solutions so, I was hoping some of you might chime in with DIY solutions that you found to be superior to other materials and solutions.
Unfortunately, I was like a greedy little kid for my Christmas list and Santa has an eye on me at least for a little while till we catch up so, gatta keep it affordable - thus, DIY!
Thank you all, looking forward to your feedback
Phil Donovan

Maybe the mods will move this to the "Record" section. I've been told Ocwen 703 boards are good. I'm going to buy a bundle of 4'x2'x2" (6 pieces) to make 3 portable panels. They sell 4" thick (3 pack) too, but for some reason the cost is a few bucks more.

[pjd3]

Thanks Barry, those panels look great for flat panels, something to keep in watch for the future. A search for those took me to a distributor that has those plus a number of other interesting materials and solutions. For now I'm looking for something good but small to line a small container with. I suppose they could be flat but I was looking for something bendable that would take the shape of a round or radiused container, bucket or something similar.

As I look at this more, maybe it is an acoustic soundproofing insulation that I'm looking for. But, thats why I'm looking into this now, to find out.

Thanks alot Barry, and nice guitar playing on your Soundcloud tracks!

Best,
Phil

[TBman]

Originally Posted by pjd3

Thanks Barry, those panels look great for flat panels, something to keep in watch for the future. A search for those took me to a distributor that has those plus a number of other interesting materials and solutions. For now I'm looking for something good but small to line a small container with. I suppose they could be flat but I was looking for something bendable that would take the shape of a round or radiused container, bucket or something similar.

As I look at this more, maybe it is an acoustic soundproofing insulation that I'm looking for. But, thats why I'm looking into this now, to find out.

Thanks alot Barry, and nice guitar playing on your Soundcloud tracks!

Best,
Phil

Thanks Phil!

You probably found this link already, but just in case:

https://www.acoustimac.com/

[Feste]

Phil,
I like your idea of a trapezoid. I considered the same thing when I was making treatments for my little studio. I also considered round columns and lots of different materials. In the end I used the Rockwool for corner traps and Knaulf Earthwool for the clouds and broadband absorption. Most materials can be cut to any shape you want. Here is a document I have posted in another thread with helpful data for various materials including the usual suspects of Owen Corning, Rockwool, etc. Absorption Coefficients (The only material I didn't find listed on this resource was Knauf Insulation-Acoustical Board with ECOSE. You can find that data here.)
This will help you decide what will work best in your space depending on what you are trying to achieve.

I wish you luck on this endeavor and keep us posted.

Another thing to consider is conducting a room analysis. Here is a video that explains how to do this fairly easily. In order to do this you will need Room Wizard Software, which is free. This link also gives you access to even more information about room acoustics.

[Earl49]

Phil, the amount of absorption (especially the lower frequencies) is directly proportional to the depth of the material. It takes a thicker material to interact with longer wavelengths of bass sound. You can take a 1" material and put it directly on the wall and an impinging sound wave "sees" essentially 2" of material (once in and once out). But space that same board out by 3" off the wall and the same sound wave sees effectively ~8" of material (two passes). Not all foam is acoustically useful either. Rigid fiberglass (OCF type 703 or 705) or rock wool board (Roxsul) is far better than most foams, and cheaper too.

When treating a room, I shoot for one treated surface on each of the x, y, and z axes. That way you are reducing the standing waves occurring along each major dimension. This will have a secondary effect of lowering the overall RT (reverberation time) for the space, making for "dry" recordings relatively unaffected by the room reverb. By the way, a perfect cube -- 1L:1W:1H -- is the worst possible ratio for critical spaces. There will be one particular standing wave that is reinforced in all three dimensions. A room that is 2:1:1 is not far behind.

[rick-slo]

Many prior threads on this topic. Suggest reading through a number of those.

[runamuck]

I'd recommend researching this issue to find out what you don't know..

Here is an excellent place to start:

https://ethanwiner.com/

[MikeBmusic]

Basically, 1" foam barely changes any sound waves going through it and bouncing back, there will be very moderate absorption of mid/mid-high frequencies. Low end and most mids won't be affected at all, leaving you with that boxy sound you heard.

[pjd3]

Thank you all for offering ideas and giving good suggestions and link resources., I will be certain to look at all of those.

To be more specific, this is primarily for recording an acoustic guitar only, perhaps a vocal occasionally so, I'm not in need of broadband absorbtion, just some mids and highs.

Also, I'm not trying to treat a room, I'm looking for something very small like a medium size bucket to line with some decent acoustic absorbent material to place various microphones into. That way, I would be a few away from the front of the opening of the lined bucket, and the bucket would be helping to just block rear, lateral and vertical reflections in the room. I don't expect an an-echoic level isolation, just a formidable reduction in the harsh slappy echos going on in all the 14' x 11' hard walled bedrooms in the house.

I'm aware that there are many searchable threads on the subject of room or portable sound isolation but wanted to see if my situation had resonated with folks who have already tried to address a similar thing. I guess I'm trying for something like those vocal isolation solutions just with vertical isolation as well - a good old bucket with good material lining it seemed like a perfect approach and something feasible for DIY home recording.

Thanks everyone! Great direction here.

[jim1960]

The only pad-like product I've ever come across that blocks sound is Acoustiblok. There may be other similar products out there but I've not come across them.

There are two issues with this approach though...
1. The stuff is expensive.
2. Blocking sound isn't the same thing as absorbing sound so I wonder about the efficacy of this as a stand alone solution. The question that needs to be answered is do membranes like this absorb sound or do they prevent it from passing through but still allow it to bounce around within the space where the sound is trapped? If the sound still bounces around, this is not a solution by itself. Room treatment would still be required.

[stephenT]

I've tried the smaller units, mic shields, etc. This works the best for me. It's movable and large enough to be effective. I stick the mic stand through the middle opening.

[jim1960]

Originally Posted by stephenT

I've tried the smaller units, mic shields, etc. This works the best for me. It's movable and large enough to be effective. I stick the mic stand through the middle opening.

The problem is the efficacy of foam is pretty low.

[stephenT]

Originally Posted by jim1960

The problem is the efficacy of foam is pretty low.

efficacy: doesn't produce the intended results.

I'm sure there are more absorbent materials, but you'd be wrong to assume my rig doesn't work in my room to shield the mics and break up bass waves.

[jim1960]

Originally Posted by stephenT

efficacy: doesn't produce the intended results.

I'm sure there are more absorbent materials, but you'd be wrong to assume my rig doesn't work in my room to shield the mics and break up bass waves.

Right. And when I said the efficacy of foam is "pretty low," that didn't mean zero. I'm assuming the foam is attached to a piece of plywood. So far as low frequencies are concerned, the plywood is reflecting frequencies, including low frequencies, but that setup has nothing that is absorbing low frequencies so those are still bouncing around in your room. The foam you're using is pretty thin. The shape of the foam will offer some minor diffusion but that foam is only going to absorb some higher frequencies.

Will it help? A bit. But if someone is going to start from scratch today to build something to improve their room acoustics, what you have isn't the best way forward. If someone is going to make the effort to build some kind of moveable solution, their time and money would be better spent building panels that will provide the most effective absorption. It will cost a little more than what you've created but the efficacy of OC703 or Roxul 60 (the materials most commonly used) is much greater.

If you search for the word "foam" on this page, the science of it is explained.