Acoustic Panels (1 Viewer)

[Dave Nibeck]

Getting ready to embark on panels. I see most people use pegboard. Would there be a benefit of using homosote (sp?) instead?

 

[ThomasW]

The masonite backs are used to make the panels stiffer/more rigid, and provide a nailing surface to attach the framing materials.

Homasote is basically a thick cardboard; so it's neither rigid, stiff, nor would it add any structural integrity to the panels.

 

[Dave Nibeck]

Thanks Thomas. I was more interested in the sound absorption properties rather than structural.

 

[TimForman]

When researching this I saw that many were using pegboard or plywood as backing material. This confused me and since I was building ceiling panels I dismissed this design based on weight considerations. I'm happy with mine but I've learned that extra absorption can be accomplished by using a reflective material behind the absorbing material. The sound passes through the absorbing material and is mostly converted to heat energy. The remaining acoustic energy is reflected back through the absorbing material and further converted so the total absorption factor is increased. With this in mind pegboard would be preferable to Homasote.

 

[Tom Blizzard]

I used this,,, without the plywood:
http://www.avscience.com/acousticpannel.htm

 

[ThomasW]

Dave

Using wall mounting for the panels, placing Homasote on the back of the panels will provide no additional sound absorbing over that already provided by the fiberglass and dacron batting.

If you're making bass traps and are spacing the panels out from the walls, then using the Homasote will increase the absorption

 

[TimForman]

Tom,
Which foam did you use? My next application of this will be wall panels but I'm thinking of using 1" polymide foam so the panel will be less intrusive in my room.

 

[Tom Blizzard]

Tim,
I used the least expensive "open-cell" egg crate type mattress foam I could find.......Also, I could not find the "soft-board" at Lowe's or Home Depot.
I did find a Georgia Pacific product called Hush-Board at a local lumber yard. Has enough body to be self supporting. It's kinda like old bulletin board material. I attached 4 foot by 4 foot panels to the ceiling using drywall screws into a ceiling joist....... Two screws per panel (with a good size washer) holds each panel just fine.

My goal was to tame first surface reflections. Sure cleaned up my home theater's sound. I also used a full wall of the panels behind my screen to make the "dead end" of my room.

 

[Dave Nibeck]

Thanks to all that replied. The panels for the side walls will probably be mounted flush to the wall. The panels for the front wall will be spaced about 4" from the wall.

Another quick question - can batting be painted? My room color is wine. I would like to go with a darker burlap and don't want the white batting to show.

 

[TimForman]

I would like to go with a darker burlap and don't want the white batting to show.

I'm not sure that will be a problem unless you're using a traditional potato sack type burlap. The burlap I purchased at the fabric store is a close enough weave that the white batting behind it is not visible. I'm using a dark green herringbone pattern burlap.

 

[ThomasW]

No never paint any sound absorbing materials.

I used muslin instead of burlap. Muslin has a tighter weave and the dacron can't be seen

 

[Tom Blizzard]

This brings up a question that I had..........

How can you determine that the fabric you want to use is acoustically transparent??

This may sound silly......... how about blowing through it?? If there is little resistance,, that's better??? If there is much resistance, not so good??

Comments??

 

[Hank Frankenberg]

The tighter the weave, the worse. Burlap is quite acoustically transparent. We had a DIY panel-building session in my garage. Used 1.4's, pegboard, and Johns-Manville rigid fiberglas, 4" thick. Hobby Lobby had about 10 different colors of burlap.

 

[ThomasW]

Acoustically transparent material is mandatory for grill cloth material where no absorption is desired.

Sound absorbing panels on the other hand are intended to suck up audible frequencies, so using acoustically transparent material is a bit counterproductive

 

[Tom Blizzard]

OK Thomas,
----------Ya gotta help me out here. I read and then reread your statement.......It "looks" like a contradiction. I just don't understand.

---------- My elementary knowledge of the subject says: wait a minute, if the cloth will not let the sound through to be absorbed, then how can the "panels" do their job?

 

[TimForman]

Burlap has some sound absorbing properties of it's own which contribute to the effectivness of the panel where an acoustically transparent material doesn't.

 

[Terry Montlick]

My elementary knowledge of the subject says: wait a minute, if the cloth will not let the sound through to be absorbed, then how can the "panels" do their job?

I agree with you, Tom. There are three things a material can do to sound: absorb, reflect, or transmit it. Any combination is possible, depending on the material. Now, if a covering fabric fully transmits sound (is acoustically transparent), then the thick absorption material behind it can work.

If, on the other hand, the fabric doesn't transmit sound well, it must be absorbing it, reflecting it, or some combination thereof.

A typical 1mm or less thickness of fabric is not a good absorber in the audio range. It is too thin compared to even short wavelengths of sound to affect them. You need more like 1/4 inch (6mm) of thickness to have a significant effect.

So thin, non-transmissive fabric is going to reflect sound, making it a bad choice as an absorber covering.

Regards,
Terry

 

[Pete Mazz]

A typical 1mm or less thickness of fabric is not a good absorber in the audio range.

Right. But it will absorb some. What TW was alluding to was that fabric that has some absorption is better for a sound absorbing panel than totally transparent material.

Highly unlikely any soft fabric would reflect sound.

Pete

 

[Chris Tsutsui]

My panels used 3.5" of fiberglass in front of pegboard. With 1/2" polyester batting on both sides of the fiberglass.

I used burlap because it is very acoustically transparent. It did cost me $1.50 per yard as opposed to 0.88 per yard of muslin. The problem with burlap is it doesn't have good color stay and fades or changes hue when exposed to sunlight like near a window.

I think that the most acoustically transparent material will work best because the sound will be absorbed by the fiberglass/polyester batting. If you use a tight weave of fabric, it should actually reflect more sound than a loose open burlap weave. I'm pretty sure it can be measured as well.

The main reason I'm using pegboard in my panels is for strength. I would rather use sound deadening board behind the fiberglass, but it is relatively flimsy.

A quick and easy panel is to use compressed fiberglass or sound deadening board cut to shape. Then wrap it with muslin using staples and secure it to the ceiling or walls with drywall anchors. It won't be as effective as a thick fiberglass or commercial thick foam panel, but it should help reduce some high frequency reflections.

 

[Pete Mazz]

The rigid fiberglass panels are about as good as it gets for absorption/thickness. Much more effective than foam and much cheaper.

Pete