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Old 3rd September 2019
  #5
Gear Addict
 

I wouldn't say I am "some knowledgeable acoustics person", more a person who over the years has aquired some bits and pieces knowledge about acoustics. Addition to above, in case you use larger sheet material instead of slats.

For reflection much would depend on the material's weight / m², for absorbtion on the "layer combination" (wood + air gap + possible insulation) plus how porous or not the outer layer is and íts stiffness which depends on distance between studs / framework (the smaller the distance the less effective as (panel) absorber as stiffness increases).

What isn't reflected is either absorbed or passing / transmitted through. In the attachements there are some clues which give some ball park figures for necessay wood thickness. The table is from 3 rd edition of Cox' & D'Antonios "Acoustic Absorbers and Diffusers." Depending on type of plywood the density varies a bit, around 500 kg/m³ could be "typical". For 1 cm thick plywood it is quite obvious it is very reflective for 1 kHz and above, 500 to 1000 Hz can be seen as a "transit region" both reflective and starting to act as a panel absorber if you compare with the figures for 9,5-12,7 mm with an air gap. For even lower frequencies the plywood gets less reflective and acts more and more like a panel absorber. The text attachement is from Kleiner's and Tichys' "Acoustics of Small Rooms". For high reflection you want a low transmission coefficient figure versus frequncies of interest.

If you use MDF as covering, paint it as MDF is a actually a bit porous.
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What frequency is reflected using 1cm thik timber slats?-foil-fabric-panel-absorbers.jpg   What frequency is reflected using 1cm thik timber slats?-wood-absorbtion-reflection.jpg