Reasons justifying a revision of the existing sound power measurement standards

It is well known that the application of the current sound power level measurement standards, even of the same grade of accuracy, lead to different results both under laboratory or even more under in situ conditions.To gain a much deeper insight on the major parameters causing differences in the sound power level measurement results the sound power levels of different sound sources were determined under laboratory conditions as well as under in situ conditions. The paper will compare the measurement results on the sound power level for different measurement setups obtained by varying parameters such as different enveloping surface shapes, different measurement probe position arrangements and sound field scanning methods both for sound intensity respectively sound pressure. The application of a transfer standard source referring to the primary standard "unit Watt" was done on purpose as to qualify the measurement setups and to allow traceability of the determined sound power levels to the primary standard.The analysis of the measurement results helps to identify main issues and to support the idea to improve the standards in respect to a more reliable usage in practice.