Acoustic Treatments, 2" inches or 4" inches thickness?

[Techlord]

Depends completely on the thread count and/or whether it's a sateen finish. I know that anything below 200TC non-sateen is definitely transparent.

Frank

I ended up going with a fabric that looks like it's woven exactly like burlap just a higher thread count to help keep the glass fibers in even if the material is disturbed. I post pictures when done.

 

[Techlord]

Well I have completed three 2' x 4' 2" thick acoustic panels and I must say I was overwhelmed by how nice they look! I plan on building three to four more, 2" thick 703 Owen's Corning. Space behind acoustic panel is 1.5" inches from wall,
fabric is just like burlap but a tighter woven to keep the glass fibers sealed and was found at my local fabric store. It cost $12.53 for six yards, ATS burlap cost me $51.56, you do the math!

 

[Weasel9992]

Wow...those do look nice.

Frank

 

[Techlord]

Wow...those do look nice.

Frank

Thanks, it's a sand stone color and is very tough fabric, hard to try and tear! It doesn't strech much which is good, they almost look pinkish in the pictures, but they are more of a brownish sand stone. I'm experimenting with placement, any suggestions?

 

[ErinH]

snipped graphs

Seems to me that you might even get good results mixing and matching types (densities). For some, thickness is a problem, so possibly buying various types of OC and layering it up would work, no?

Also, I had read once way back (I don't even recall where, now) that not only mixing densities is a great benefactor, but also mixing the pattern direction as well (ie: pattern 1 goes up/down, pattern 2 goes side/side). Been a while since I've looked at fiberglass of any sort, but if there is a pattern direction then this seems to be logical as it would (presumably) cause the sound waves to have to go through more work before hitting wall which it is mounted to and thus result in a higher STC?

 

[ErinH]

Furthermore, Floyd Toole touches on the use of various materials for various reflection control in his “Sound Reproduction” book.

This being the most important aspect:

High-density boards tend to become reflective for high-frequency sounds arriving at angles approaching grazing incidence. As the material gets thicker, the low-frequency performance improves. However, to be effective at bass frequencies, these devices become impractically large (approximately 1/4-wavelength deep). We need another way to absorb energy. Membrane (mechanically resonant) absorbers are the most popular absorption mechanism for low frequencies. This happens when a surface moves in response to sound, mainly low-frequency sound. Energy is expended to move the surfaces, and less is returned to the room. Normal floors and walls therefore are useful membrane absorbers, and, to a limited extent, it is possible to optimize
their contributions in controlling room resonances.

Emphasis added… think about this for the absorption of low end response…

Further reading leads me (and maybe I’m misunderstanding so I implore anyone not to take my post as Gospel) to believe that one way to do broadband absorption is using a mix of materials. Maybe even something as simple as a layer of ¾” mdf (due to it density and absorption of low end response) with a layer of a fiberglass type over it (for mid-high frequencies). Of course, this is ONLY an idea. I may give it a shot soon but will continue to do more reading as to not waste time (and money) on these efforts.

Another bit of info:

In summary, all of this suggests that the surface of the absorbing material—the interface with the sound field—should have relatively low density and that to achieve performance at lower frequencies, one may need to seriously consider how much real estate can be devoted to the task because materials that work well have appreciable thickness. The problem is the damage inadequately thick materials do to the sound quality of reflected sounds from loudspeakers. The appropriate fabric covering appears to have little effect at low and mid-frequencies, but it becomes refl ective at high frequencies, especially for sounds approaching from angle, as in the case of sidewall reflections.

The typical “acoustical” fabrics are not grille-cloth; they are acoustically translucent, not transparent. This means that loudspeakers should not be placed behind them. If they are stretched across a section of wall, even a blank wall,
and spaced away from the wall, they will function as absorbers—admittedly, not very good ones. Some installations, however, have large areas treated in this manner, so the audible effect can be significant. In home theaters, it is not
uncommon for walls to be sheathed in fabric chosen by an interior decorator, with little or no concern for what it may do to the performance of acoustical devices and materials underneath.

I don’t want to clutter this thread anymore, but let’s not forget absorption and diffraction differences, too.

Ultimately, this is what Toole has to say on the subject:

One can debate the pros and cons of first reflections, but if the decision is to eliminate such a reflection, then there are two options: absorb it with a thick resistive absorber (not less than 3–4 in. (75–100 mm)), or diffuse it with a thick diffuser (not less than about 8 in. (200 mm)). The criterion in both cases is not the thickness itself but the need to maintain high levels of acoustical performance down to 300 Hz or below.

 

[jostenmeat]

Emphasis added… think about this for the absorption of low end response…

Further reading leads me (and maybe I’m misunderstanding so I implore anyone not to take my post as Gospel) to believe that one way to do broadband absorption is using a mix of materials. Maybe even something as simple as a layer of ¾” mdf (due to it density and absorption of low end response) with a layer of a fiberglass type over it (for mid-high frequencies). Of course, this is ONLY an idea. I may give it a shot soon but will continue to do more reading as to not waste time (and money) on these efforts.

I think it depends on the room. Sure, bass absorbers are very large (and that's why you see superchunk corner traps), but in some rooms, the modal intensity can be so much, that absorbing higher midrange frequencies themselves might be a very worthy goal. I believe I've read that a larger room will have less issues with bass, but that it deals with greater HF reflectivity. Don't quote me on that. Anyways, my own room, and home for that matter, is much more problematic with midrange/HF than bass, IMO (not measured). There is also the Helmholtz resonator, that some people cleverly hide into a riser's structure, for example.

Another bit of info:



I don’t want to clutter this thread anymore, but let’s not forget absorption and diffraction differences, too.

Ultimately, this is what Toole has to say on the subject:

Did you instead mean diffusion? It seems that many experts lean towards absorption over diffusion for most applications and budgets.

 

[ErinH]

Nope. I did mean diffraction.
But, honestly, as far as I know, they're one in the same in this context. Diffusion is how you hear diffraction. At least, that's how I've come to know it.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/diffrac.html

 

[harry121]

home theater floor sound proofing and what is right size of home theater

My home built panels are 4" deep, but use 2" acoustic fiberglass. It creates a 2" gap in the back to assist in a broader range of freq absorbsion. The front and back of the fiberglass is covered in quilting batting with speaker cloth over the front.

(Basically I followed Tom's guide to building acoustic panels

HI,PLEASE TELL ME what is good material for flooring how we sound proofing the floor in better way .my room is 16 fit wide and 10 fit height what is right length size.i have 12 fit place .

 

[harry121]

sorry i have 16 fit wide ,10 fit height and 34 fit long space .what is ideal room length

 

[Chitown2477]

I just found this YouTube video that shows you how to assemble the 4" panel without the plywood backing, it uses the fabric on the front of the frame then wraps the fabric around the acoustic material stapling it onto the back frame. I understand how to make it now, 4" it is! I like the idea of having the acoustic material exposed by 2" inches for extra absorption.

Thank you Mike again,

Techlord.

So if a frame is used with the fabric or material on the front, what cover the back? Looking to build some panels myself and would like to know.

Also where is the best place to buy the Owens Corning materials, Home Depot?

Thanks in advance for information!!

 

[bpape]

If you're going to use a frame on the rear, just staple some muslin on the front of the frame where you'll be placing the absorption. Then when you wrap it, it's a nice clean look on the rear and the wood is still exposed for easy mounting.

As for the previous discusson on acoustic transparency, don't get too hung up. AT is only critical when placing in front of speakers as long as the fabric is still somewhat breatheable and doesn't act like a membrane reflecting some frequencies.

Muslin and even the Guilford Anchorage series are just fine for treatments, though not so for grilles in false walls and columns where speakers are behind them. They will attenuate the tweeter response more than is desirable.

Bryan

 

[jostenmeat]

If you're going to use a frame on the rear, just staple some muslin on the front of the frame where you'll be placing the absorption. Then when you wrap it, it's a nice clean look on the rear and the wood is still exposed for easy mounting.

As for the previous discusson on acoustic transparency, don't get too hung up. AT is only critical when placing in front of speakers as long as the fabric is still somewhat breatheable and doesn't act like a membrane reflecting some frequencies.

Muslin and even the Guilford Anchorage series are just fine for treatments, though not so for grilles in false walls and columns where speakers are behind them. They will attenuate the tweeter response more than is desirable.

Bryan

Bryan, I just bought a 10yd roll of "utility speaker cloth" from Joann's for a future false wall, and as my "black backing" to my future AT screen. Any thoughts or experiences? I should be fine, yes? Thanks.