Egea-Valero J., Bernardes A.

The European Organization for Nuclear Research (CERN), the world's largest particle physics centre, is currently installing its new particle accelerator, LHC (Large Hadron Collider). This new generation particle accelerator will become the most powerful ever constructed, with the start up in 2007. Noise and its impact on the environment is a well know problem of large scale industrial plants. In relation to this subject, CERN has started a noise mapping and modelling study of the 9 access sites to the underground that spread out into the populated areas between Geneva and Jura mountains, where all necessary infrastructures (more than 400 acoustic sources to model) for the LHC operation are housed. This work aims at predicting the noise impact of the infrastructure currently being installed for the LHC. The study has taken place in two stages. A measurement campaign was done in order to get the data of acoustic sources such as large scale cooling towers, electrical substations or compressor halls for the world largest liquid helium refrigerators. In a second step, CERN has used experimental acoustic software, TYMPAN 3.2, developed by EDF (Electricité de France) to carry out the noise mapping, control the noise impact and validate possible solutions. After a brief description of the principles, this paper shows the acoustic model of a typical CERN installation. The noise map is validated by comparing to « in situ » measurements. Then, the paper presents an acoustic analysis of the calculated sound levels, describes the acoustic treatments envisaged and evaluates their effects on the noise map. Finally, conclusions are drawn on the application of this type of acoustic tool for dealing with noise impact problems.