Lignotrend Sound Absorption Results
Sound Absorption Results of LIGNO Acoustic Light 3S-33
using Various Constructions
LIGNO Acoustic Light 3S – 33 (Installation on battens / suspended)
What does the Sound Absorption Coefficient Mean?
The sound absorption coefficient of a material α tells us how much of the incident sound has been absorbed by the material, rather than reflected back into the room. If the absorption coefficient α is 0, none of the sound has been absorbed by the material and it has all been reflected back into the room. If α is 1, the entire original sound has been absorbed by the absorption material and no reflection will occur. An absorption coefficient of 0.5 indicates that half of the sound wave has been absorbed. The absorption rate varies according to the frequency of the sound wave and the following table is an indication of the absorption abilities of some common building materials.
|Building Material||Typical Sound Absorption Coefficient across frequency range – 125 to 4000 Hz|
|Bricks, unpainted||0.00 – 0.05|
|Carpet, heavy on foam rubber||0.30 – 0.55|
|Concrete block, unpainted||0.05 – 0.35|
|Concrete block, painted||0.05|
|Cotton insulation, 100mm||0.95 – 1.3|
|Curtains, depending on weight||0.05 – 0.6|
|Timber floor||0.05 – 0.2|
|Glass||0.05 – 0.10|
|Seating (occupied)||0.80 – 0.85|
|Seating (unoccupied), metal or wood||0.30|
|Seating (unoccupied), fabric upholstered||0.60|
|Wood fibre insulation board, 20mm||0.05 – 0.77|
The reverberation time depends on a number of factors:
- The volume of the room
- The surfaces in the room
- The furniture in the room
- The number of people in the room
As you can see from above the greater the number of absorbing surfaces within the room such as heavy curtains, thick carpets and upholstered seating, the better the absorption rate. The reverberation time is also reduced when there are more people present in the room. Rooms with high ceilings usually have longer reverberation times, unless they have been acoustically treated.
What are Absorption Classes?
Absorption classes A to E are described in EN ISO 11654. The classes are determined by comparing the weighted αw values to a series of fixed reference curves. So an A class is very absorptive and an E class is very reflective.
|Weighted Sound Absorption
|A||0.90 – 1.00|
|B||0.80 – 0.85|
|C||0.60 – 0.75|
|D||0.30 – 0.55|
|E||0.15 – 0.25|