ISO 11654 and Calculation of the Rating of Sound Absorption
About the ISO 11654 Standard
The ISO 11654 is the internationally recognized standard that specifies methods fo calculating the rating of acoustic absorption of materials. The measurement of sound absorption is based on the ISO 354 and the ISO 11654 is used to calculate the rating and the class.
How the sound absorption is measured?
The sound absorption is measured according to the ISO 354 in a laboratory. The material (a
surface around 10m²) is placed in a reverberant room.
The reverberation time is measured with and without the materials inside the room and by
using the differences between the 2 reverberation times (with and without the materials),
the sound absorption of the
material is calculated.
This is the calculation of the equivalent absorption area AT (in
m2)
for each one-third octave band
\[ A_T = 55.3 \times \left(\frac{1}{c_2 \, T_2} \;-\; \frac{1}{c_1 \, T_1}\right) \;-\; 4 \times V \times (m_2 \;-\; m_1) \]
- V: Volume of the room in m3
- c: Speed of sound in air (m/s). Typically c = 331 + 0.6 × T, where T is the temperature in °C (15 °C < T < 30 °C)
- T: Reverberation time in seconds
- m: Power attenuation coefficient in m–1, calculated according to ISO 9613-1
- m1: m1 = α / (10 × log(e))
From AT, the absorption coefficient αs (Dimensionless) for each one-third octave band :
\[ \alpha_s = \frac{A_T}{S} \]
- S: Surface area of the sample in m2
What are the different ratings presented in the ISO 11654?
Based on the measurement of the sound absorption presented above (αs), the ISO 11654 gives the calculations methods to evaluate :
The table below presents how the class is defined:
Sound absorption class | αw |
---|---|
A | 0.90; 0.95; 1.00 |
B | 0.80; 0.85 |
C | 0.60; 0.65; 0.70; 0.75 |
D | 0.30; 0.35; 0.40; 0.45; 0.50; 0.55 |
E | 0.25; 0.20; 0.15 |
Not classified | 0.10; 0.05; 0.00 |
How to use the different ratings from the ISO 11654?
First, these different ratings are used to have a quick representation of the sound
absorption performances. It's used also to compare products between them.
However, for
acoustic studies, the measured sound absorption in third octave or octave are
used.
How to use our tool AcouVApp Abso Rating
The tools is quite easy to use. You just need to copy/paste your data in the table by
putting your mouse key in the first row.
The calculation is automatically done when you change the values in the table. Be carrefull
to
enter correct values (from 0 to 1 and sometimes little more than 1).
You have also acces to the shifted curve below the graph.