Helmholtz/Panel absorbers

I came across these pics on a uk studio design company page.It would seem at first viewing that the silver wall panels are helmholtz absorbers,if so can anyone give me some idea as to the frequencies affected were I to copy them.I am assuming the panels are lined with absorbent and made from wood and the silver ones metal.Will the wood ones act as panel absorbers.I have been on the www.mhsoft.nl/Helmholtzabsorber.asp web site but the max diam for holes is 15mm.How would larger holes as in pic affect performance.I love the wall to wall treatment on attachment and plan to copy it using timber for the panels.

Those are pretty cool looking panels, and do appear to be helmholz traps - however, that specific site (and most others) is using an INCORRECT formula for calculation, at least for the slat resonator - so was the SAE site, one of the people on studiotips.com discovered this several months ago. I've emailed to the site you linked twice in the past few months advising them of the incorrect formula, and it's still WRONG. For slat absorbers, here's the correct version - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=1363 And for inches instead of metric - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=1781 I've not had time to check their perforated absorber info out, and probably won't for quite a while - still, I'd be careful about blind acceptance since apparently around 90% of the calculators on the web are using this incorrect formula (someone typo'ed a "+" in place of a "*" in the formula, and everyone else blindly copied it) Generally, larger holes equate to higher frequencies affected - however, with a perforated panel (slats too, actually) it's really the percentage of perforation compared to total panel area that's defining. On my corrected versions, I left the old formula in place for comparison - highlight both the incorrect and correct frequency cells, and compare formulas - the only diff is the one operator being a + instead of a * - If you into the math at all, you might be able to tell whether a perforated panel calculator is correct by comparing formulas, If I'm not mistaken the formulas are similar because you're comparing panel area to perforation area with EITHER type of absorber... Steve

Thank you once again for the advice knightfy and for the links.

someone typo'ed a "+" in place of a "*" in the formula

Excuse me for the layman type question, I am not a math expert by any means. What does the symbol * mean? Does it represent multiply? Thank you!

While at first glance one might think those are Helmholtz absorbers, they are in fact highpass filters for the hidden absorption, and diffusers. Andre

mr. torture wrote:

someone typo'ed a "+" in place of a "*" in the formula

Excuse me for the layman type question, I am not a math expert by any means. What does the symbol * mean? Does it represent multiply? Thank you!

euh, yes it does. In computerland the asterix symbol "*" is what you proly know as the multiply symbol "x". so: 2*4=8 (on PC) would be the same as 2x4=8 (on calculator, human writings etc)