Title: Productive measurement of transmission loss characteristics using Nearfield Acoustic Holography
text: A continuously growing demand comes from the automotive industry for optimisation of materials and sound insulating products implementation inside the car, in order to propose the best acoustic performance at reduced costs. As already presented last year at SEA Brazil [9], the approach based on extensive use of the acoustical holography system dBVISION of 01dB-METRAVIB provides part of the solution to such a demand. Whereas the first paper was dedicated to some general considerations and practical aspects of NAH implementation inside a car, the one proposed for the 2005 session is focused on a very important aspect of NAH measurements, namely productivity, for both inside and outside measurements. The paper reviews the NAH technique advantages for measuring the acoustic field inside and outside a vehicle and performing extensive studies on transmission loss characteristics of panels and car openings, with the aim of: detailed localization of possible acoustic weakness points on single components, ranking of the tested components in terms of global and partial radiated power contribution driving possible optimisation of component in the early stages of the design cycle The applied test set-up will be presented and its main features regarding productivity improvement will be highlighted, with a special attention to the compact and versatile robotized instrumentation used for this type of measurements. The presentation will be illustrated by operational results in different situations and some possible extension will be proposed in order to open this technique to the efficient characterization of 3D-shaped structures.