ISO/IEC GUM applied to estimation of sound power measurement uncertainties

Abstract

The methods to implement ISO/IEC Guide to the expression of uncertainty in measurement (GUM) and the ISO engineering grade sound power standard are provided. The sound sensitivity coefficients are partial coefficients of the sound power and the combined standard uncertainty is the summation in quadrature of all uncertainty contributions to the sound power. Each uncertainty contribution is calculated from the measurement standard deviation and the sensitivity coefficient. ISO also puts a limit on a decibel range of the measures sound levels and this range is equal to the number of measurement points. Sound pressure obtained on an very large planar measurement surface very close to a very large piston can give a good estimate of sound power. It is shown that when the environmental correction is zero, the worst case sensitivity coefficient is 1, with the resulting worst case sensitivity contribution of 2.3 dB.