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Old 24th May 2020
  #7
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You are to funny.
Quote:
Originally Posted by gearstudent View Post
There was no discussion to continue. The advice given was "go read a book", and was done so in a dismissive way. The actual question was not answered.
My reply was "You have so many misconceptions. Read the chapter Absorption in MHoA." You obviously did that from the following

Quote:
I found this in the Alton Everest book:
"The mounting method has a major effect on the absorption characteristics of the material. For example, the absorption of porous materials is much greater with an airspace between the material and the wall."

Also from the Alton Everest book:
"Effective low-frequency absorption can also be achieved by spacing the porous absorbent out from the wall. A spaced porous absorber can be as effective as a non-spaced absorber of the same thickness. This is an inexpensive way to get improved performance—within limits."

I saw corresponding airspsace-is-good statements repeated among several acoustics materials companies, and did not find any other academics or industrial entities with contrasting statements. So my conclusion, based on statements of multiple professional sources, is that a reasonable amount of airspace behind an absorber panel is not harmful, and is even helpful.
For people not familiar with all of Everest's writings that is like from the chapter on absorption in Master Handbook of Acoustics (MHoA).