[Eapiel]

I am toying with the idea of using 1/2 inch medium density fiber board in lieu of 1 inch thick linacoustic material for our basement theater ceiling. Whatever material I go with, I will then install ceiling tiles (probably Frost tiles from USG) over the mdf or linacoustic using the ceiling max grid system.


I am considering the mdf because:


-- mdf is thinner (1/2 inch vs 1 inch) , and will save on my 7 foot ceiling ht.


-- mdf is cheaper per sq ft than linacoustic panels and more readily available.


-- I will screw the mdf panels in place in 2 X 4 foot sections so I will still have access to ceiling piping, lighting and wiring, WHEN that becomes necessary. This is why I prefer not to drywall.


-- One disadvantage of mdf is the overall weight. Linacoustic will obviously be much easier to install.


What I am not able to find is the NRC and CAC equivalent ratings of medium density fiberboard. How will MDF compare to ceiling tiles and linacoustic?

 

[LooseChange]

The question is, is MDF as efficient at absorbing sound than rigid fiberglass? Somehow I don't think it would be. I used to have the link to the site that showed the acoustic properties of a ton of building materials but lost it in the shuffle. That'd be a good place to start to compare the two.

 

[relwof]

Quote:

Originally posted by LooseChange The question is, is MDF as efficient at absorbing sound than rigid fiberglass? Somehow I don't think it would be. I used to have the link to the site that showed the acoustic properties of a ton of building materials but lost it in the shuffle. That'd be a good place to start to compare the two.

WARNING: I'm guessing here, so use at your own risk!


My guess would be that MDF rather sucks at _absorbing_ sound. It is "too" rigid, kind of like brick or concrete. However, it will probably do well at reflecting (i.e. blocking and returning to the room) a good bit of sound, especially mids and highs. Also, I would think that _maybe_ MDF is more "dead", i.e. less resonant, than something like plywood (less "drum" effect) I did a DIY soundproof studio door out of 3/4" MDF on one side and particle board on the other, with a 2x4 (1.5" deep) framed cavity inside the door completely filled with sand. It was quite effective...


If you're looking at soundproofing, I'd be wary of MDF, except as a skin for other layers. And trust me, you DON'T want to try that door trick on your ceiling panels, unless you have something like 12" steel I-beams for joists and some masochistic body-builders giving you free help to trim their gym bills...


Finally, what exactly do you want your ceiling to do? Soundproofing (reducing the sound escaping the room) and sound "conditioning" (tuning the acoustic response of the room) are really two separate challengs. Usually your priority is some combination of the two, but it helps to know which is more important!


- james

 

[Eapiel]

I wish I was manly enough lift a sand filled mdf door onto the ceiling as you describe there relwof. But I think I can handle one sheet of mdf...maybe


I am looking for a reflective ceiling. The website Loosechange refers to http://www.saecollege.de/reference_m...nt%20Chart.htm lists all sorts of materials, but not mdf. It does list plywood and gypsum or drywall. The numbers, if I am reading them correctly, seem to indicate gypsum is more effective at reflecting sound than plywood, which I hope is somewhat close to mdf characteristics.


I am hoping mdf may be a good compromise (isolation, some absorption, and retaining access to the ceiling plumbing), but I really do not know for sure...

 

[Diver]

Insulation on walls helps tame reflections.

Insulation in walls helps capture sound (all but the bass) that has passed through the wall surface.

MDF is much heavier, which will help tame bass, if the sheets are not directly fastened to the structural members of the home.


Higher frequencies are easier to stop (Keep inside of room). Think of them as ping pong balls bouncing around inside of your room. Fiberglass insulation and foam work well enough to tame these.

Low frequencies require more effort to capture. Think of them as bowling balls bouncing around inside of your room. When a bowling ball hits a wall, the energy of the impact passes through the wall structure, moving the other side of the wall, transmitting the sound. To minimize this:

- Add more mass to the inside wall (2nd layer of sheetrock, MDF, other)

- Decouple the inside of the wall from the outside (resilient channel on the inside wall sheetrock, stagger stud, or double wall).


If you are trying to keep sound from escaping the room, screwing 2x4 panels to the ceiling has challenges:

- Every joint is a place where air/sound can escape, so the joints must be sealed with silicone.

- Sound transfer from the MDF to the ceiling rafters/2nd story joists needs to be decoupled (same as walls). Resilient channel is one option.


Every material has a point where it resonates at a certain frequency. Two pieces of anything side by side will produce an unpleasant resonating sound at some frequency. If you choose to use 2 layers of sheetrock, or attach MDF to the ceiling, be sure to use screws rather than nails, and use a construction adhesve between the layers to glue them together.