What is sound absorption?
Sound absorption is an important concept in room acoustics. Creating spaces that are both visually appealing and healthy to be in is of paramount importance in both private and professional life. Sound insulation is material that prevents sound from penetrating (sound is reflected) while sound absorbing materials allow sound to pass through with attenuated strength.
Absorption
Soundhitting a surface loses energy through friction and this energy is converted into heat - this is called absorption. However, there is so little energy in the sound that it is impossible to perceive any heat.
Fabric-covered acoustic screens are effective sound absorbers that work in this way. How much is absorbed depends on the density, thickness and fibre structure of the material.
Reverberation time
The acoustic properties of differentrooms can be explored by measuring the reverberation time, i.e. the "echo effect". A sound is generated and the various surfaces in the room reflect the sound and the sound waves bounce straight back, resulting in a diffuse echo. The time from when the sound is switched off until the sound subsides, i.e. decreases by 60 dB, is the reverberation time. The reverberation time and the volume of the room can then be used to calculate how much a given amount of sound absorption reduces the reverberation time.
Diffusion
By using reflective surfaces that can "scatter" the sound, unpleasant echoes can be avoided - this is called diffusion. Wall absorbers are often of this type.
Attenuation
Inan office environment, for example, you often see screens placed between workstations to shield and reduce the sound level from one side to the other. Properly designed and positioned, such a screen can reduce the noise level by about 10-15 dB between two workplaces. A standard wall typically attenuates 35 dB or more.
