Acoustic effectiveness of fabric systems
The acoustic properties of a component are tested using a so-called reverberation chamber. With the aid of measured reverberation times, the frequency-dependent sound absorption of a sample body is measured. The sound absorption rate aS indicates how much effective sound absorption area A corresponds to a square meter test area. The larger aS is, the better the sound absorption rate aS is. The sound absorptivity of a material is determined separately for each third-octave band. In order to measure a specific material configuration for its acoustic effectiveness, the configuration is constructed having the prescribed dimensions according to EN ISO 354 (2003) (a contiguous area of twelve square meters) stretched over a module system. In the reverberation chamber, this system is subjected to a frequency from 0 to 5000 Hz. The profile obtained gives an indication of the frequency-specific and the averaged sound absorption coefficient (aW). The frequencies between 300 and 700 Hz are of interest to most room acoustic problems because they reflect most of the everyday sounds. High frequencies are relatively easy to absorb, but unfortunately also of little relevance, since they are usually not of a disturbing nature. The average value is therefore only conditionally conclusive. The main focus is on the overall curve from which the frequency-specific absorption coefficients emerge. A comparison of the curves then gives a statement about the acoustic effectiveness of the individual material configuration and whether this ultimately meets the requirements as an acoustic system.