Sound power level measurement in reverberant room: Estimating the uncertainties and their laboratory use

Certification programs and accreditation of test laboratories require an estimation of the uncertainties of acoustic measurements. The “Guide to the expression of uncertainty in measurement” (ENV 13005) offers an interesting approach to the estimation of uncertainties and is commonly applied to other fields of physics in addition to acoustics. The GUM method was used to estimate the sound power measurement uncertainty of liquid chilling packages in a reverberant room. The independent quantities were identified and included in the propagation law of uncertainty, showing the importance of both standard uncertainty and sensitivity coefficients. Their study allowed us to sort out uncertainty components and then to quantify their influence on the uncertainty associated with the one-third octave band values as well as the overall sound levels. These analyses provided working methods for improving the quality of the laboratory measurements, which showed that the sound source and microphone locations are the main factors affecting the final uncertainties.