The flow resistance is the force with which a matter opposes a movement. The specific flow resistance Rs is measured. The value is shown in Pa*s/m or Ns/m3. A good flow resistance value starts at 800Pa*s/m.
Sound absorption describes the reduction of sound energy especially (but not necessarily) by turning sound into heat or movement. “Absorption” equates to “swallowing” and “soaking”. The sound produced in a room spreads as an airborne sound wave and meets room boundary surfaces, which partially absorb the sound and partially reflect it.
The sound absorption grade aw describes the ability of a matter to absorb sound.
- αw = 1 = 100% complete sound absorption, no reflection
- αw = 0 = 0% no sound absorption (which means complete sound reflection)
- ideally one achieves a value of 60% / αw = 0,6
- the measurement takes place in a sound room according to DIN EN ISO 354
- one measures the reverberation time with and without the fabric sample in order to determine the absorption grade
- evaluation process: according to DIN EN ISO 11654
- classification into absorber grades A, B, C, D, E
- A = extremely highly absorbing, with a sound absorption level αw: 0,90…1,0
- B= highly absorbing, with a sound abortion level αw: 0,80…0,85
- C = highly absorbing, with a sound absorption level αw: 0,60…0,75
- D = absorbing, with a sound absorption level αw: 0,30…0,55
- E = low absorbing, with a sound absorption level αw: 0,15…0,25
- Not classified, sound absorption level αw: 0,00…0,10