Technical and Applied Papers ACTA ACUSTICA UNITED WITH ACUSTICA Vol. 100 (2014) 1186 – 1201 DOI 10.3813/AAA.918797 Repeatability and Reproducibility of In Situ Measurements of Sound Reflection and Airborne Sound Insulation Index of Noise Barriers Massimo Garai 1) , Eric Schoen 2) , Gottfried Behler 3) , Beatriz Bragado 4) , Michael Chudalla 5) , Marco Conter 6) , Jérôme Defrance 7) , Patrick Demizieux 8) , Christ Glorieux 9) , Paolo Guidorzi 10) 1) DIN, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy. massimo.garai@unibo.it 2) TNO, 3700 AJ Zeist, The Netherlands. eric.schoen@tno.nl 3) RWTH Aachen University, Neustraße 50, 52066 Aachen, Germany. gkb@akustik.rwth-aachen.de 4) CIDAUT, Parque Tecnológico de Boecillo, P209,47151 Boecillo (Valladolid), Spain. beabra@cidaut.es 5) BASt, Brüderstrasse 53, D-51427 Bergisch Gladbach, Germany. chudalla@bast.de 6) AIT, Giefinggasse 2,1210 Vienna, Austria. marco.conter@ait.ac.at 7) CSTB, 24 rue Joseph Fourier, 38400 Saint-Martin-d’Hères, France. jerome.defrance@cstb.fr 8) LRPC Strasbourg, 11, rue Jean Mentelin - BP 9, 67035 Strasbourg cedex 2, France. patrick.demizieux@developpement-durable.gouv.fr 9) K.U. Leuven, 24 Celestijnenlaan 200D, bus:2416, 3001 Leuven, Belgium. christ.glorieux@fys.kuleuven.be 10) DIN, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy. paolo.guidorzi@unibo.it Summary In Europe, in situ measurements of sound reflection and airborne sound insulation of noise barriers are usu- ally done according to CEN/TS 1793-5. This method has been improved substantially during the EU funded QUIESST collaborative project. Within the same framework, an inter-laboratory test has been carried out to assess the repeatability and reproducibility of the newly developed method when applied to real-life samples, including the effect of outdoor weather variability and sample ageing. This article presents the statistical analysis of the inter-laboratory test results, and the values of the repeatability and the reproducibility, both in one-third octave bands and for the single-number ratings. The estimated reproducibility values can be used as the extended measure of uncertainty at the 95% credibility level in compliance with the ISO GUM. The repeatability and re- producibility values associated with airborne sound insulation are also compared with the corresponding values for laboratory measurements in building acoustics and an acceptable agreement is found. PACS no. 43.58.Gn, 43.58.Vb, 43.50.Gf, 43.55.Rg 1. Introduction Noise barriers are one of the most frequently used means to reduce the impact of noise emanating from roads, rail- ways and factories. Amongst their most important char- acteristics are their ability to not reflect part of the inci- dent sound energy, and to reduce sound transmission from the noise source on one side to the neighborhood on the other side. These characteristics can be assessed with lab- oratory tests under a diffuse sound field [1, 2]. The Eu- ropean project ADRIENNE made it possible to measure these characteristics in situ under a direct sound field [3]. In Europe, in situ measurements of sound reflection and airborne sound insulation of noise barriers are currently done according to CEN/TS 1793-5 [3, 4]; a separate new Received 27 September 2013, accepted 15 July 2014. normative standard has recently become available for air- borne sound insulation [5]. This method has been validated by several authors, but the repeatability and reproducibil- ity of the method has been only occasionally estimated and reported in the literature [6, 7, 8, 9]. The in situ method has been substantially improved during the EU funded QUIESST project [10, 11, 12, 13]. Moreover, in the same framework, an inter-laboratory test (ILT) has been carried out in order to assess the repeatability and reproducibility of the newly developed method when applied to real-life samples [13, 14, 15]. In this article, the most relevant aspects of the QUIESST inter-laboratory test are discussed. The values for repeata- bility and reproducibility are presented, both in one-third octave bands and for the single-number ratings. The val- ues are also compared, whenever possible, with the cor- responding values for laboratory measurement methods. Finally, some recommendations for future standards are presented. 1186 © S. Hirzel Verlag · EAA