Page 12 - Laqfoil Acoustic Catalog

Sonorous Room
Dead Room
Comfortable Room
A sonorous room is one in which the reverberation continues for an uncomfortably long period of time. Multiple sound reflections become superimposed upon each other, creating noise.
A dead room is one with an uncomfortably short reverberation time. This can be more of a problem with conversation than with music in the room. When the reverberation time is just right, we call this optimal reverberation. In acoustic terms, this is a comfortable room.
The theory of sound absorption by porous materials was developed John William Strutt, 3rd Baron Rayleigh, (12 November 1842 – 30 June 1919), an English physicist, in his book The Theory of Sound (Volume I: London : Macmillan, 1877, 1894, Volume II: London : Macmillan, 1878, 1896), which is still used by acoustic engineers today.
His theory was based on the fact that there are viscous forces in porous materials which prevent air from passing easily through the pores. This resistance thus takes away part of the kinetic energy from particles of air which are vibrating with sound, turning it into heat.
According to this theory, the absorptive properties of porous materials depend on the viscosity and density of the air, and the number and radius of pores per unit area. Using a porous material as a coating material for a solid wall, the thickness of
the layer of material, or, to be more precise, the distance between the
porous surface and the solid wall determines the amount of sound absorbed. As well, the smaller the pores’ radius and the more
there are of them, the better high frequencies are
absorbed.
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