The most frequently used measure of the acoustical quality of a room is reverbera- tion time. Reverberation times are computed following various standards including ASTM C423, in which the decay of sound is measured. Experimental modal anal- ysis is a procedure typically used on plates and shells in which loss factors, modal masses, resonance frequencies, and mode shapes defining the object are extracted using measured frequency response functions (FRFs). These methods may be ap- plied to reverberant rooms to measure low frequency reverberation times using loss factors.
Results of the characterization of the reverberation chamber in Penn State’s Center for Acoustics and Vibration (CAV) are presented. Reverberation times, levels of background noise, and five ideal measurement locations that give results matching those of the overall chamber are among the topics discussed. The results of a modal analysis experiment performed in the reverberation chamber are also presented. A modal overlap factor (MOF) of 1 is found to be below 125 Hz, indicating that the chamber is reasonably diffuse at and above that level. While the Schroeder frequency is found to be 378 Hz. The extracted loss factors are related to the reverberation times and compared to the results of the ASTM tests. The results compare favorably, with the reverberation times from the modal study being slightly lower.
