Quantifying repeatability, reproducibility, and bias in sound power level measurement methodologies via a round-robin study

This paper presents results from an interlaboratory study to examine 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. A loudspeaker playing both a broadband signal and a broadband signal with four discrete tones has been measured in participating laboratories according to the standardized test methods that are commonly used in each facility. Results across 1/3 and 1/1 octave bands are then compared between signals, between methods, between laboratories, and across all laboratories using the same method. Additional discussion regarding potential sources of variation between facilities is presented. Ultimately, in accordance with ISO 5725, repeatability, reproducibility, laboratory bias, and test method bias are estimated. To reduce uncertainty of these estimates for some methods, additional laboratory participants are needed. [Work supported by the Air-Conditioning, Heating, and Refrigeration Institute.]