Characterization of a removable, hemianechoic floor in Health Canada’s large anechoic chamber

Abstract

Health Canada is interested in promoting the use of quieter industrial machinery through sound power measurement and labeling. To measure sound power under standard hemianechoic conditions, a removable floor was installed and tested in the anechoic chamber. The floor had dimensions 13 m× 9 m and was constructed from 2.8-cm-thick concrete tiles. It was designed to have a sound absorption coefficient below 0.06 in the range 50 Hz–20 kHz, as required by sound power measurement standards. Characterization of the acoustical performance using ISO3745 indicated that measurements were acceptable to a distance of more than 2 m. In situ estimates of the absorption coefficient using acoustic intensity showed the local absorption coefficient could be improved by sealing the joints in the floor. The intensity technique also showed that below 125 Hz, the absorption coefficient was limited by the floor dimensions. In situ vibration measurements of individual floor tiles suggested that the absorption coefficient was acceptable under acoustical excitation. Floor vibration and reradiation of sound power can be a problem in any room. Calculation of sound power radiated from the floor using vibration measurements (ISO/TR7849) was found useful for determining if a source should be vibration isolated.