Fabric as room treatment

[rockinrocker]

Not sure if this is the right forum or not, but here goes;

OK, from what I understand fabric/curtains can work well for room treatment, as long as it's heavy enough. Is that correct? Are there any other considerations here? What type of material and so on?

I have access to a large piece of heavy fabric that i'm thinking of covering with muslin left over from covering my rock wool in order to make a large, heavy curtain.

And also, being some distance away from the wall will actually increase effectiveness, right?

Basically, the space I'm trying to cover is a sort of recessed area that's about 15' long and about 4' deep. Would it work well to hang my "curtain" over that area in order to tame reflections and the like?

Thanks.

[SixAndChange]

It will work, but only on varying particular frequencies. What you'll want to do is figure out the dimensions of you room, where your mix position will be, and the average distance between various aspects of your room.

Your looking to affect frequencies over 300 Hz with materials such as cloth, and foam, and other types of softer material. Each one has its own absorption coefficient, which will vary between 1.00 (full absorption), 0.50, (half absorption), all the way down to 0.0 at which point equals full REFLECTION.

These levels are found by calculating how much each individual material can reduce sound energy that has been moved into it.


Material Sound Absorption

Coefficient - α

Plaster walls 0.01 - 0.03
Unpainted brickwork 0.02 - 0.05
Painted brickwork 0.01 - 0.02
3 mm plywood panel 0.01 - 0.02
6 mm cork sheet 0.1 - 0.2
6 mm porous rubber sheet 0.1 - 0.2
12 mm fiberboard on battens 0.3 - 0.4
25 mm wood wool cement on battens 0.6 - 0.07
50 mm slag wool or glass silk 0.8 - 0.9 12
mm acoustic belt 0.5 - 0.5 Hardwood 0.3
25 mm sprayed asbestos 0.6 - 0.7
Persons, each 2.0 - 5.0
Acoustic tiles 0.4 - 0.8

These are just various general examples, and it is important to remember that the aC is frequency dependent.


Offhand I believe a heavy carpet added to a dense surface would provide .14 to .65 amounts of absorption from 500Hz to 4kHz, gradually becoming more efficient as the wavelengths become shorter (higher) and shorter.

These are fairly simple to fix with materials as you noted, but can sometimes have the affect of completely killing any live sound or doing absolutely nothing at all.


What would be desirable for what is most likely a smaller rectangular room, would be to have good amount of diffusers (spreading sound out) AND absorbers. This way your room does not take on the characteristics of a dirty sack of laundry.

Lower frequencies are a totally new ball game, but you mentioned rockwool so I think you're taking care of that rather well .


Just for kicks though, here is a fun, free and simple program that gives you an average guess of which axial (parallel surface) modes youre likely to encounter.




You simply input your room dimensions (height, width, length) and it wil give you three individual graphs of what kind of standing waves to expect in an untreated room.

Here is the link for the free download.

http://www.realtraps.com/modecalc.zip


If anyone has anything different to say or add in I'd love to hear it!



Good luck, and post some pictures!