Beschreibung:
<jats:p>Many measurement procedures for sound absorption rely on approximations or necessitate special restrictions. The measurements in the tube usually only cover small samples and rely on a plane wave at normal incidence of sound. Reverberation chamber measurements assume diffuse sound fields and other constraints. Furthermore sound absorbers might show local or non-local reaction, e.g., angle dependence of the acoustic surface impedance or not. The performance of sound absorbers, either in a room or outdoors, often involves neither plane sound waves nor diffuse sound fields. This is one motivation for the development of measurement procedures applicable where the sound absorber is actually used, namely, in-situ methods. The paper will present a short historical review on the development of measurement techniques of sound absorption or the acoustic surface impedance. Measurement examples will be shown for some of the methods presented and compared to each other.</jats:p>