Commercial perforated ceiling tiles.

[Zaphod]

These days in the Italian home theatre forum i read, a guy posted
the specs of some perforated panels, that seem quite good...

(here is the post he made: http://www.avmagazine.it/forum/showpost.php?p=1046004&postcount=20)

and there is the website for the stuff...

http://www.acustica-edilizia.it/gyptone_plank.htm

I played with Chris' porous absorber calculator getting graph much
more bell shaped, but it does not work perfectly on openoffice, so
i'm not really sure of the result.

The guy asked if he should go with the stuff and i advised him
against, being a tuned device, what do you think?

The graph on the site are so flat for the medieval band limited
graph or for some other reason?

[Eric.Desart]

The guy asked if he should go with the stuff and i advised him
against, being a tuned device, what do you think?

That you're wrong,
.....and that you should base yourself and your decisions on these absorption curves in that doc, which are typically for such stuff.
But take into account that also cavity and absorption material plays a roll.

.

[bert stoltenborg]

Hey wrong Zaph,

there is some paper about perforated panels on the net. Maybe SuperBob knows where....



I found it on my HD, I could send it if you PM your mail adress. It's 5.5 MB, if you're interested.
You're not totally wrong, behaviour depends on how the perfs are done.
But  this ceilings are broadband.

[Terry Montlick]

A ceiling cavity vs. none makes a huge difference. ASTM A mounting is flush against the surface, while ASTM E-400 mounting has a 400 mm (16") air space to the hard surface, a typical ceiling cavity depth. The latter sort of mounting can turn the most mediocre acoustical tiles into stellar wideband absorbers!  :mrgreen:

Regards,
Terry

[bert stoltenborg]

A ceiling cavity vs. none makes a huge difference. ASTM A mounting is flush against the surface, while ASTM E-400 mounting has a 400 mm (16") air space to the hard surface, a typical ceiling cavity depth. The latter sort of mounting can turn the most mediocre acoustical tiles into stellar wideband absorbers!  :mrgreen:

Regards,
Terry

Almost as stellar as a Super Chum!

[Zaphod]

Ooops  :oops:


The graphs are with 200 mm airgap.

Not having such space, he plans (i think an installer pointed him
that way), to wall mount them with a 45mm cavity all filled with rockwool
or the equivalent.
That's because he wants to absorb bass and has no space for big
chunks or deep absorbers.

Ok, now i have to run and take back what i wrote  :mrgreen:    

[Zaphod]

Hey wrong Zaph,
I found it on my HD, I could send it if you PM your mail adress. It's 5.5 MB, if you're interested.
You're not totally wrong, behaviour depends on how the perfs are done.

If it's easy and filled with picture, feel free to mail them  :mrgreen:

Does not one have to compensate for >4khz frequencies? (not a
difficult problem, i'd say)

[Bob]

Bert:

One of these ?? :

http://www.iperf.org/IPRF_ACAPPS.pdf
http://www.iperf.org/IPRF_ACUSES.pdf
http://www.iperf.org/IPRF_CD.pdf
http://beteq.engineeringconferences.net ... ction2.pdf
http://www.bbc.co.uk/rd/pubs/reports/1992-10.pdf

[bert stoltenborg]

Cool, Bob!

[Eric.Desart]

Bert,

You refer to an arbitrary doc, without naming it. Just referring to Bob who must have a Crystal ball
I get curious.

Bob as mostly does some work, entering links to documents, hoping somewhere in-between is the doc you have in your mind.
You just reply with "Cool".

I still can not analyze what you were talking about.

Is it possible for you to refer to a doc, just giving it a standard reference as a name and an author?
That way people with standard working mental processes can follow as well.

[gullfo]

hee hee he said "mental"  8O

[bert stoltenborg]

It was something with that iperf, Eric.
I found it on my HD, but alreasy lost it again.

[Eric.Desart]

Thanks Bert,

If you compare this stuff, it's still important to take into account that the perfo sheet in these docs from iperf have large holes compared to thickness, while this slotted or drilled gypsum board stuff are small holes versus thickness, hence more subject to the Helmholtz stuff.

 And thanks to Bob once more, for his assistance in finding the answer on a non-defined question.

[Ido]

I found it on my HD, but alreasy lost it again.

 :D  :D


Zaph, a major thing with perforated gypsum board is that it has a an absorptive cloth lining in the back, which helps it work "better", whatever that means.
if used smart, these "simple" things can be good, cause they don't overabsorb HF.

[Pop Alexandra]

If find it a bit easier to perforate the ceiling panels myself, as sometimes the stock perforations don't fit the project, but I've heard a lot of people being happy with the perforated ones, too.