sound absorption eng.ivaylo hristev. contents 1.normal and diffuse sound absorption coefficient. 2....
TRANSCRIPT
Sound absorption
Eng.Ivaylo Hristev
Contents
1.Normal and diffuse sound absorption coefficient.
2. Sound absorber types:
•Porous absorbers
•Membrane absorbers
•Resonance absorbers
Normal sound absorption coefficient
Diffuse sound absorption coefficient
Diffuse sound absorption coefficient
Porous absorbers – open cell structure
Closed cell structure
Open cell structure
Source Cremmer&Muller 1978
Closed look of real world materials
Porous absorbers – open cell structure
Closed cell structureOpen cell structure
Porous absorbers – typical examples
Porous absorbers – thickness
Diffuse absorption coefficient of polyurethane foam with the same density and different thickness; source Cox&D’Antonio 2004
Simulated diffuse sound absorption coefficient of mineral wool with density 50kg/cub.m. and various thickness.
Porous absorbers – thickness
Porous absorbers – air cavity thickness
Simulated diffuse sound absorption coefficient of mineral wool with density 50kg/cub.m. and various air cavity thickness.
Porous absorbers covered with thin layer
Diffuse sound absorption coefficient of mineral wool with density 60 kg/cub.m. covered with 0.1mm polyethylene.
Porous absorbers – applications
Porous absorbers – applications
Membrane absorbers – construction
Membrane
Porous absorber
Air cavity
Rigid backing
Membrane absorbers
Diffuse sound absorption coefficient of a membrane absorber with various membrane thicknesses with and without rockwool.
Simulated and measured sound absorption coefficient of a membrane absorber; source Cox&D’Antonio 2004.
Membrane absorbers
Membrane absorbers - application
Resonance absorbers – Helmholtz absorber
Resonance absorbers – perforated panels
Small holes shallow depth
Large holes shallow depthSmall holes big depth
Large holes big depth
Resonance absorbers – perforated panels
Resonance absorbers – perforated panels; effect of the open area
Perforated panels – applications
Perforated panels – applications
Perforated panels – applications
Which type of absorber?
Which type of absorber?
Weighted sound absorption coefficient αw is calculated according to EN ISO 11654. Measured sound absorption coefficient αs is averaged in 1/3 octave band frequencies as αp according to EN ISO 354. Then the values are compared to a standardized curve.
Weighted absorption coefficient
The same standard EN ISO 11654 classifies the sound absorbers into different classes. ISO 354 absorption coefficient αp is compared in which region fits.
Sound absorption classes
Questions?