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Post by NigelSpiers on Mar 31, 2016 10:34:16 GMT
Hi, Do these panels really absorb 70-75% of all sound (see following link)? hushpanels.co.nz/products/suspended-ceilings/Given that only 27% of their surface area is open to sound absorption. I note they have a layer of Polyester sound absorption material behind the wooden panel - but that panel only absorbs 70% of sound when fully exposed to the sound not when 73% hidden behind wood. I'm confused - please advise how these panels work. Thanks & Best Regards
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Post by Rock on Mar 31, 2016 11:30:56 GMT
Looking at the graphs, these may be some sort of Helmholtz slat resonance absorber.
Cheers, Rock
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Post by NigelSpiers on Mar 31, 2016 12:54:09 GMT
Yes - I Agree they appear to be Helmholtz resonance absorbers but does this type of product really work to the NRC levels they are claiming?
I thought that Helmholtz absorbers with one hole size were designed to absorb only one frequency.
I also note from their frequency charts that there are some unusual and significant looking troughs and peaks.
I have tended to shy away from recommending Helmholtz absorbers because logic told me that they are a pretty round-a-bout, inefficient and expensive way of taming acoustics in a room.
However if I'm wrong I'd like to know more about them.
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Post by Ethan Winer on Mar 31, 2016 18:03:56 GMT
Looking at the C1.20 model, it doesn't absorb very much except for part of the midrange.
I have to admit that I'm not up on the math or theory for slotted absorbers.
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Post by Rock on Mar 31, 2016 21:16:57 GMT
Compare the NRC data to that of rigid fiberglass or mineral wool. At the very least, FG or MW will likely have a flatter curve and extend to the high end, if not more/better NRC overall ... depending on the thickness.
Cheers, Rock
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Post by Hexspa on Apr 2, 2016 23:01:14 GMT
Compare the NRC data to that of rigid fiberglass or mineral wool. At the very least, FG or MW will likely have a flatter curve and extend to the high end, if not more/better NRC overall ... depending on the thickness. Cheers, Rock ...and density
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Post by NigelSpiers on Apr 3, 2016 21:26:48 GMT
Hi - thanks for your thoughts - another question:
OK - I understand that the 50mm polyester acoustic panel on the back of the slotted wooden panel will absorb some (limited) sound.
But what if there is no Polyester panel - just the slotted wooden panel with one hole size and a gap of say 50mm behind it - how much sound (NRC rating) at a what frequencies will it absorb?
Thanks for your advice
Nigel
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Post by Rock on Apr 4, 2016 12:19:32 GMT
Here's a site with many online calculators for resonant absorbers that you can experiment with to help answer your question. Sorry, I did not find any indication of NRC in the results. www.mh-audio.nl/acalculators.asp#showcalcUnless my requirement was specifically for a narrow or bandwidth limited absorber because I already had enough absorption in other bands, I would use a wideband porous absorber, the thicker, the lower the frequency. I'm going with the idea that equal absorption across the audio band will yield equal RT 60s.
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