This European Standard specifies additional necessary information on how to carry out efficiently and under standardized conditions the determination of the sound absorption coefficients according to EN ISO 354 “Measurement of sound absorption in a reverberation room”. It specifies the additional requirements of the sound absorption measurements and the operating and mounting conditions that should be used for the test. Observe that all demands in EN ISO 354 still should be fulfilled. The results obtained are used for design calculations with respect to room acoustics and to convert frequency-dependent sound absorption coefficients into a weighted sound absorption coefficient aw, according to EN ISO 11654. This European Standard is applicable for the compile of the single number rating aw, to express the sound absorption performance of suspended ceiling membranes in CE marking and labelling according to EN 13964. This European Standard is not applicable for suspended ceiling kits according to EN 13964.