Sound Absorption Measurement: Alpha Cabin and Impedance Tube

Abstract

The stage of development of absorbent materials, when necessary to verify their properties in relation to established requirements, plays one of the key challenges in current research. Nowadays, experimentation represents the only reliable way to quantify sound absorption. Thus, the determined sound absorption coefficient is used to compare individual development variants, and also, it is used in a selection of material from the commercial offer. Therefore, the main part of research is devoted to measurements in the impedance tube and in the alpha cabin, because these procedures play one of the most challenging roles in practice. All used experimental methods are based on the theory about transformation of sound energy into other forms of energy in the material. Nevertheless, the physical nature of sound absorption and individual measurement principles are not covered in this chapter, nor are any sound insulation measurements. It deals solely with the sound absorption and determination of the sound absorption coefficient. As a results, this chapter further summarizes basic information on a sound absorption measurement, and mainly, focuses on practical recommendations as well as applicability of results. First and foremost, these individual procedures may represent a considerable international overlap in the field.