An independent method for the measurement of sound power, based on a primary standard traceable to units tied to fundamental constants, has been realised and tested. The most important achievement is that the uncertainty evaluation can be deduced in a direct and (mostly) analytical way from the primary standard and measurement environment parameters, both hemi free and reverberant acoustical fields have been considered. A new traceability line to the primary standard has been established, and the validity of the already available transfer standards has been investigated. All these achievements have the revision of the sound power measurement procedures, for which developments and validation has been carried out during the project, as a goal. Dissemination has been realised by papers, participation in conferences and a seminar. Future work will focus on improvement of the frequency range and uncertainty of the primary standard, establishment of measurement capabilities by means of key comparisons in the EURAMET region, declarations of services in the CIPM database and proposed revision of the ISO standards concerning sound power. Another important task is working among the acoustic industrial and metrological community to foster the acceptance of the new methods. Applications to calibration of microphone arrays are also possible.