The document specifies a method by which the frequency dependent values of the sound absorption coefficient can be converted into a single number.
DIN EN ISO 11654:1997 history
2018DIN EN ISO 11654:2018 Acoustics - Sound absorbers - Rating of sound absorption coefficients (ISO/DIS 11654.2:2018); German and English version prEN ISO 11654:2018
1970DIN EN ISO 11654 E:2017-10 Sound absorption classes of sound absorbers used in acoustic buildings (draft)
1997DIN EN ISO 11654:1997-07 Acoustics - Sound absorbers for use in buildings - Rating of sound absorption (ISO 11654:1997); German version EN ISO 11654:1997 / Note: To be replaced by DIN EN ISO 11654 (2017-10), DIN EN ISO 11654 (2018-05).
1997DIN EN ISO 11654:1997 Acoustics - Sound absorbers for use in buildings - Rating of sound absorption (ISO 11654:1997); German version EN ISO 11654:1997