Can i stack several acoustic ceiling tiles?

michaelv · « **on:** 27 May 2005, 02:20 pm »

Hi,
i went to Home Depot the other day and i saw Armstrong acoustic ceiling tile s (2'x4'). It's about 1/4" thick and NRC=0.55

I was wondering whether i can stack 2 or 3 of this acoustic ceiling tile together to make acoustic panel and increas NRC a bit? ( i mean NRC will be increase to more than 0.55 if stacking the tiles together?). I think this is a cheap solution i can think of .

thanks.

ctviggen · « **Reply #1 on:** 27 May 2005, 02:35 pm »

You will increase the NRC, but the increase might not be linear (meaning that 0.32 + 0.32 might not be 0.64).

JoshK · « **Reply #2 on:** 27 May 2005, 02:48 pm »

I think csero did just what you are suggesting.

michaelv · « **Reply #3 on:** 27 May 2005, 02:48 pm »

THanks, ctviggen

Ethan Winer · « **Reply #4 on:** 28 May 2005, 03:40 pm »

Michael,

> I was wondering whether i can stack 2 or 3 of this acoustic ceiling tile together to make acoustic panel and increas NRC a bit? <

Yes that works, but you want to remove the plastic facing from all of the tiles.

Also, the absorption is not increased per se. What really happens is the absorption is extended to a lower frequency. That is, one tile absorbs 100 percent at, say, 2 KHz and above, and using 2 tiles extends that down to 1 KHz. Double it again to four tiles and now they absorb 100 percent down to 500 Hz. And so forth.

--Ethan

michaelv · « **Reply #5 on:** 28 May 2005, 03:51 pm »

Ethan,
The acoustic ceiling tile i see at Home Depot does not have plastic facing. This tile is the same drop down ceiling at the office building. It's kind of compact powder , not the fiberglass one.

Each tile has NRC=0.55 . Which NRC number level do you suggest to reduce the refelection of mid/high? and how many tile should i put together to make it effective to the level you would suggest? My room is echoed and i want to reduce that. Sorry to ask questions that might have been asked .

thanks.

Ethan Winer · « **Reply #6 on:** 28 May 2005, 09:10 pm »

Michael,

> The acoustic ceiling tile i see at Home Depot does not have plastic facing. <

In that case, never mind.

I was talking about the 5/8 inch ceiling tiles Home Depot has that are made from rigid fiberglass. That's the only kind I can personally vouch for. The paper-based type of tiles surely absorb, but 1) probably not very well at higher frequencies which is important for first reflections, and 2) I've never measured that material in a lab so I can't say for sure how well they work or what happens when they're stacked.

Part of the problem is that NRC data is meaningless for music purposes because it considers only the speech frequency range. What's needed is absorption data in octave or, better, third octave bands.

--Ethan

michaelv · « **Reply #7 on:** 29 May 2005, 10:20 am »

Ethan,
I see what you mean now. I went to HD and found Armstrong acoustic ceiling tile. It's 5/8" thick and made of yellow rigid fiberglass, which also has plastic facing. I will get some and try the first panel today.

thanks.

Ethan Winer · « **Reply #8 on:** 29 May 2005, 02:47 pm »

Michael,

> I went to HD and found Armstrong acoustic ceiling tile. <

Exactly. Stack 3 together for mid/high absorption, and enough to get 4 inches thick for bass trapping in the room corners, and you'll be good to go.

--Ethan

michaelv · « **Reply #9 on:** 29 May 2005, 07:52 pm »

For bass trap, do you mean that i just make a same panel like the one for mid/high and put in the corner? Do i need to stuff anything behind the corner panel?

If i want to make a box, which material do you suggest? I am thinking of building a triangular box and stuff fiberglass inside.

thanks.

Red Dragon Audio · « **Reply #10 on:** 29 May 2005, 09:06 pm »

Not exactly.

The mid/high trap Ethan says to stack 3 of them which would be 5/8" x 3 which is just shy of a couple inches thick.

To make bass traps out of these ceiling tiles you need to stack them to achieve 4" or greater thickness which means you need about 7 of them.

Something to think about is finding a supplier of rigid fiberglass panels in your area. This should save you time, money and will certainly save you some headaches as you won't have to peel, glue and stack tiles together to make bass traps. Just cut them to desired size and cover in fabric or paint to match the room.

Just a thought for the bass traps and maybe even for the mid/high panels.

Ethan Winer · « **Reply #11 on:** 30 May 2005, 04:22 pm »

Ryan,

Exactly!

--Ethan

michaelv · « **Reply #12 on:** 31 May 2005, 01:47 pm »

Thanks for comments, Ethan and Heavystarch.

It's hard to find fiberglass in my area. The only online dealer who carries it is insulationworld.com .But, the cost of fiberglass + shipping + handling is way too expensive. So, i guess i have to do the hard way by sticking several pieces of rigid fiberglass (5/8") that i've found from Home Depot.

One question : Do i have to peel plastic sheet from every single fiberglass or just the first one which faces the room?

For bass trap, Can i make it small size of 1'x4' (4" thick)? And do i need to stack them from ceiling to floor?

thanks very much.

Ethan Winer · « **Reply #13 on:** 31 May 2005, 02:27 pm »

Michael,

> the cost of fiberglass + shipping + handling is way too expensive. <

When you consider that room acoustics is more important than pretty much anything else, I have to ask how much you spent on your speakers and other gear.

> Do i have to peel plastic sheet from every single fiberglass or just the first one which faces the room? <

Yes. Plastic in between the layers will reduce its effectiveness.

> For bass trap, Can i make it small <

Not if you want it to work well! Acoustic treatment, and especially bass trapping, is all about coverage. The larger the total surface area, the better the results.

--Ethan

Red Dragon Audio · « **Reply #14 on:** 1 Jun 2005, 04:05 am »

Hi Michael,

You should contact Scott F. here on AC. He used to work in the industrial insulation supply business and might be able to point you towards some local distributors in your area that you might not have been aware of.

If he can't find any for you, then you will have to go with the Home Depot plastic peeling route.

michaelv · « **Reply #15 on:** 1 Jun 2005, 01:40 pm »

thanks, heavystarch and Ethan.

i have second thought that i will install both fiberglass ( i now need only 2 panels) and acoustic foam (i have some from foambymail.com) . By the way, what does the following number mean?

Freq NRC
125 Hz .13

250 Hz .29
500 Hz .89
1000 Hz 1.08
2000 Hz .97
4000 Hz 1.04

Overall NRC = .81

These above numbers are from Wedged Foam (2 " thick) . Since i need to treat my ceiling as well, should i use these wedge or the this http://www.foambymail.com/DropCeilingTiles.html to treat the echo in ceiling? The Drop Ceiling tile is 2" thick , but i'm torn between wedged or drop ceiling to make it more effective

The drop ceiling has overall NRC = .7 It has less NRC than wedge with the same thickness, but it look nice and neat for the ceiling.

thanks

Ethan Winer · « **Reply #16 on:** 1 Jun 2005, 03:32 pm »

Michael,

> what does the following number mean? <

If the numbers came from Foam by Mail, unfortunately they mean nothing. It has recently been proven that Foam by Mail sells cheap packing foam - not real acoustic foam - and they faked all of the data on their site.

Normally, with a reputable vendor, this type of data tells how much a material absorbs at various frequency ranges. If you're interested in learning more about how acoustic materials are tested, see THIS article on my company's web site.

--Ethan