An inter-laboratory study to quantify the repeatability, reproducibility, and bias of sound power measurement methods

An inter-laboratory study across multiple facilities has been completed to quantify the repeatability, reproducibility, and bias of three different sound power measurement methods used in the heating, ventilation, and air-conditioning industry: free field method, diffuse field method, and intensity method. The sound power levels of a loudspeaker source across one-third octave bands have been measured in each participating laboratory by the test methods preferred in those facilities. Both a broadband signal with decreasing slope of - 5 dB per octave band and the same broadband signal with four discrete tones at 58, 120, 300, and 600 Hz have been measured in this round robin study. Comparisons of measured sound power levels have been made between methods, between laboratories, and between laboratories using the same method. Repeatability, reproducibility, laboratory bias, and test method bias are then quantified in accordance with ISO 5725. [Work supported by the Air-Conditioning, Heating, and Refrigeration Institute]