Sound power determination by intensity-Are field indicators and criteria in ISO 9614 meaningful?

Abstract

The three parts of ISO 9614 describe methods for the determination of the sound power level of noise sources. According to these standards, measured sound power levels must be qualified by comparing several sound field indicators to given criteria. This procedure is investigated by analytical calculations with monopole and dipole sources. Their sound fields are superposed with extraneous free and diffuse sound fields. When the ISO 9614 method is applied to these cases, it turns out that the signed pressure intensity indicator is well suited to qualify the measured sound power level. In contrast to this, the unsigned pressure intensity indicator and the field non-uniformity indicator fail to describe the quality of the determined sound power level. This theoretical finding is verified by a large measurement program.