Traceable sound power measurements in essentially diffuse or free fields

Current methods for the determination of sound power such as the ISO 3740 series do not have a direct traceability to a primary standard. The different methods are regarded as equal, but they do give results with systematic differences. One task of the European project "EMRP JRP SIB 56 SoundPwr" has been to develop and investigate traceable and consistent methods for sound power measurements in essentially diffuse or free fields. By using a calibrated reference sound source as a traceability source, qualification procedures for setups for sound power determinations in different environments have been investigated. Uncertainty sources such as sound field sampling, directivity, frequency content and impedance of the device under test have been analysed. For sound power determinations by using sound intensity a substitution method has been developed. The results are presented in the contribution.