Abstract
Absorption of acoustic wave is due to viscous and thermal
losses and relaxation processes in fluid: - Absorption is
emphasized near boundaries, especially in small holes,
slits and narrow tubes, - Viscous losses dominate with
small free space dimensions: -Perforated /
microperforated plates, - Absorbing materials: "Holes"
and "slits" described by fluid bulk properties (flow
resistivity, porosity, tortuosity, viscous andthermal
characteristic lengths).
Sound transmission of a wall is due to two parallel
transmission paths: - Non-resonant and resonant
transmission, - Below coincidence frequency non-resonant
transmission dominates except in the resonance region.
With double walls above double-wall resonance, sound
insulations in dBs are summed with reasonable amount of
absorption in cavity if mechanical coupling is
insignificant.
Original language | English |
---|---|
Publisher | VTT Technical Research Centre of Finland |
Number of pages | 45 |
Publication status | Published - 2014 |
MoE publication type | D4 Published development or research report or study |
Keywords
- sound absorption
- sound insulation
- physical mechanisms