A Mobile Reverberation Cabin for Acoustic Measurements in an Existing Anechoic Room

Large reverberation rooms are generally prescribed for the acoustic characterization of materials. Diffuse-field absorption properties are measured in a reverberation room, while transmission loss properties can be measured between a reverberation source room and an anechoic receiving room. The large volumes needed (ASTM standards require 80 m3) make the building of such rooms impractical, and transforming existing anechoic rooms in transmission suites is generally impossible.In the present work, a mobile reverberation cabin is developed and placed into an existing anechoic room for acoustic material characterization. Light materials (plywood and wood) are chosen to enable an easy assembly and disassembly of the cabin. An external thick layer of open-cell foam is used so as not to compromise the anechoic properties of the surronding room. The interior dimensions of the cabin are taken from a similar design in the existing literature: no walls are parallel, and the interior volume of the cabin is less than 1 m3.The sound field measured inside the lightweight mobile cabin is presented, and a lower frequency limit is determined for its diffuse field behavior. A procedure for the characterization of acoustic samples in absorption and transmission loss is defined, and validated with known materials.