# The distribution of absorptive panels



## pitchtwit (Apr 11, 2011)

I need advice on the distribution of absorptive panels in rooms that need a very low reverberation time (rehearsal rooms for pop/rock music that is very loud).

I work at a music college that has just got use of four new rehearsal rooms. They installed absorptive panels that are very large - ceiling to floor - each one about 4' wide - in no particular location - sometimes just covering one wall, with one or two walls left completely uncovered. The total coverage in each room is roughly 1/3 of the walls with nothing on the ceiling. The absorptive paneling appears to be pretty high grade stuff - it's dense, black, with a specially shaped surface - I think it was expensive.

Anyway, the sound in the rooms is pretty bad and we requested more absorptive paneling. Unfortunately they can't afford more of the same stuff, so they've started making large panels in-house using wooden frames with rockwool (or something like that) covered by an open-thread material to hold it in. They're about 2' by 4'. In one of the rooms they've installed 7 of these - 4 on the ceiling and 3 on the walls, and the sound hasn't really got that much better - although it has improved.

I recently suggested that they should cut the high-grade stuff up into 1' by 1' squares and distribute this evenly around the room. I'm doing an acoustics Masters at Salford Uni in my second year (part time) so I know a bit about it. I was going to find some evidence about the best way to distribute absorption in a room, but I thought I'd just ask on here first in the hope that there are a load of good resources that you guys already know about.

Any links to articles etc. would be greatly appreciated.


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## bpape (Sep 14, 2006)

What are the dimensions of the room?

What is the thickness of the material that they originally put up and are putting up now?

Bryan


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## pitchtwit (Apr 11, 2011)

I don't have the exact details of anything I'm afraid. The rooms are generally about ~2m high, ~3-4m wide & ~3-5 m deep. The walls are just plasterboard at the moment - not sure about the ceiling. The floor is under-carpet tiles of some sort.

The thickness of the initial absorption treatment foam is about 1". They're a bit like this - http://www.soundcontrolservices.co....oducts_id=30&zenid=jav6ikm05i093v1q0isqq8eal4


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## bpape (Sep 14, 2006)

Unfortunately, what they bought is doing little to nothing. First, foam only is going to do upper mids and highs. Second, 1" isn't thick enough to do much so highs only. What is needed for a band is more like 4" thick and something with a good core like fiberglass. 

I would say they'd want a minimum of 20-25% coverage if not more and that's assuming the thicker, more broadband treatments.

Bryan


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## pitchtwit (Apr 11, 2011)

Many thanks

:T


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## pitchtwit (Apr 11, 2011)

btw, i found a great paper on the distribution of home made absorption panels for people on a budget. i basically says that putting them in the corners of your room (diagonally - not flush to the walls) gets you a much more broadband level of absorption than if they're flush against the walls. i'm sure you knew that, but it's always good to be able to point people towards things like this so i thought i'd let you know about it.

It's called Acoustical Tests of Custom-Made, Low Cost Bass Absorption for Small Rooms by Ioana Pieleanua, Jeffrey Fullertonb and Marc Choinierec.

It's free to all here: - http://asadl.org/poma/resource/1/pmarcw/v4/i1/p015001_s1?bypassSSO=1

Or here's the direct download address: -
http://scitation.aip.org/getpdf/ser...dtype=cvips&doi=10.1121/1.2988051&prog=normal

:T


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## bpape (Sep 14, 2006)

Tried both links with Firefox and nothing. Was just going to go through it and make sure it's accurate before we recommend it to folks.

Bryan


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## pitchtwit (Apr 11, 2011)

Hmm, I checked it in my Firefox and Safari before I posted. It works now in both for me too. I'll put them again here anyway: - 

http://asadl.org/poma/resource/1/pmarcw/v4/i1/p015001_s1?bypassSSO=1

Direct download: -

http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PMARCW000004000001015001000001&idtype=cvips&doi=10.1121/1.2988051&prog=normal

Also, seeming as it's free to anyone I'll put it in my public dropbox too: -
Acoustical Tests of Custom-Made, Low Cost Bass Absorption for Small Rooms by Ioana Pieleanua, Jeffrey Fullertonb and Marc Choinierec (2008)

:T


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## pitchtwit (Apr 11, 2011)

The dihedral corners around the top (or even bottom) of the room would presumably give a similar result.


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