Contribution
Absorption coefficient measurements in rooms with different volumes
* Presenting author
Abstract:
Sound absorption measurements according to ISO 354 are performed in reverberation rooms with a volume of about 200 m³. These measurements suffer from an upper frequency limit (5 kHz whereas 10 kHz would be desirable, e.g. for predicting an STI) and a relatively large uncertainty. The upper frequency limit is mainly due to air absorption which is also one cause for the large uncertainties at the highest frequencies. As many laboratories for building acoustics have test rooms with a volume of about 50 m³ at hand, it is of interest to investigate if using such a room in addition to a reverberation room could improve the situation. In a first step, the participants of comparison measurements at PTB were asked to measure the absorption coefficient of a broadband absorber, with the upper frequency extended to 10 kHz, in a room of 53,6 m³. Subsequently, an internal round robin was conducted, where eight different absorber setups were each measured in five different rooms by individual measurement teams for each room. Prior to the measurements, all rooms were fitted with diffusers following the procedure described in ISO 354 Annex A. The results and conclusions will be presented.