Definition

An acoustic absorbent material is a material in which sound waves penetrate and then are dissipated. There are two main families of absorbent materials: fibrous materials and porous materials.

Fibrous Acoustic Material
Porous (Foam) Acoustic Material

Differences Between Fibrous And Porous

On both cases, the material will absorb sound if the acoustic waves are able to penetrate the material.

  • If the material is too dense or cells are closed, the acoustic waves will bounce off the surface.
  • If the material is too open or very sparse, the acoustic waves will penetrate it but will not be dissipated.

In the case of a porous material, there must necessarily be a network of interconnected pores, also called open porosity. In the case of fibrous materials, the fibers must have a small thickness and must be dense enough to allow the dissipation of acoustic energy. There is therefore a certain compromise for the material to be considered absorbent.

The dissipation of acoustic energy can be done by heat transfer, by viscous dissipation or by inertial effect by setting the skeleton of the material in motion.

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