• RE: Absorption coefficients of building materials - KlausR. 10:45:43 01/07/11 (0)
  In Reply to: RE: Absorption coefficients of building materials posted by Hifisound on January 07, 2011 at 09:02:17

  The problem with reflections is that if you want to get rid of them, or at least lower their level to below perception threshold, you need broadband absorbers. Floyd Toole advises to use stuff that goes down to 150-200 Hz, which in the case of porous absorbers means 42-57 cm thickness for total absorption.
  
  But the question is: are reflections in general and the floor reflection in particular a problem? You did not mention anything, why do you want to tame the floor reflection, is there any particular reason? There is no scientific evidence that reflections are a problem as a matter of principle. They may be in individual cases.
  
  Alternatives? If you do need to treat the floor reflection, then I would first calculate what thickness is necessary for porous absorbers to get the level of the reflection below perception threshold, so you'd need psychacoustic data. For music the threshold is, depending on music motive, between about 10 and 18 dB below the level of direct sound. Everest should provide equations to calculate what thickness of what material you need to lower the reflection level by say 15 dB.
  
  You mentioned blocking the reflection by using furniture. Sound waves have the tendency to move around obstacles so I'm afraid that will not work either. You could re-direct the reflection by using angled panels, but again, for low frequencies the panels will have to be large.
  
  Klaus
  

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