# ceiling tile nrc rating question



## corock (Sep 7, 2009)

I found these great inexpensive ceiling tiles on line. They come in lots of great patterns like the one pictured, and are available in black. But they are made from rigid vinyl. The website says the NRC rating is 25-30%...how does that compare with normal ceiling tile that I would buy at Home Depot? 

Also I plan to use 3 matching LCR speakers, so there won't be a horizontal center channel.


----------



## bpape (Sep 14, 2006)

NRC isn't something you should really even worry about. It ignores a lot of the musical spectrum. It's more a measurement for voice, footfall, etc.

Bryan


----------



## corock (Sep 7, 2009)

The fact they're rigid vinyl concerns me. The company will send free samples. Is there a way to measure its reflection vs a standard ceiling tile with my Dayton EMM-6 mic?


----------



## bpape (Sep 14, 2006)

If they're rigid vinyl, they'll be pretty much 100% reflective above probably 1kHz. That's not necessarily a bad thing depending on how the rest of the room is treated. 

Bryan


----------



## tubamark (Jun 25, 2009)

corock said:


> I found these great inexpensive ceiling tiles on line. They come in lots of great patterns like the one pictured, and are available in black. But they are made from rigid vinyl. The website says the NRC rating is 25-30%...how does that compare with normal ceiling tile that I would buy at Home Depot?
> 
> Also I plan to use 3 matching LCR speakers, so there won't be a horizontal center channel.


I've gotten some of their samples. They are extremely thin and flimsy, unable to even hold their own shape unless supported by a grid. You can even see a some light thru the black ones. Whatever sound they are "absorbing" is by sympathetic vibration (membrane absorber)and/or absorption provided by the space above the grid - not the tile. Acoustically, they are useless, except for very high-frequency scattering. Not a sound investment for any home theater, listening room, or studio I've ever seen.

NRC can be very misleading, as it is an average of absorption over a very limited frequency range. Actual absorption can be very inconsistent, with a peaky response. Having said that, here are some general guidelines:

An NRC below ~.55 is not considered absorptive.
An NRC between .55 and .75 will still allow you to "hear" the ceiling, unless it is pretty high
An NRC above .85 is preferred for an 8' ceiling
An NRC of .95 to 1.0 is possible from 1" thick fiberglass tiles - _strongly_ recommended for ceiling less than 8'. This NRC is not possible with typical mineral board tile.

Your typical home-store tiles are not ideal, with NRC's mostly in the .45 to .70 range.

There are excellent NRC tiles available, but not in a home store. Usually have to be special-ordered. Often, a contractor distributor will often get you a better price than a home store.

For a high NRC (~.95) white ceiling, try USG Nubby or USG Halcyon tiles. If you are looking for a flat-Black high NRC ceiling, please PM me. Whatever you do, don't buy the painted black ceiling tiles (or paint your own) -- the NRC is very poor.

-- Mark


----------

