Use of Heterogeneous Microphone Triplets for Simplified Noise Apportionment in Pass-By Measurements

Localization of different noise sources in a high-speed train has been endeavored in the past with reasonable success. In most cases, this localization has been achieved by means of microphone arrays and also with the help of fixed or removable barriers. However, these techniques had the drawback of needing complex post-processing and frequently have complicated set-ups. Also, very often the assessment obtained with these methods has been predominantly qualitative, and not quantitative. High speed railways have the distinctive feature (with respect to conventional railways) of emitting significant amounts of aerodynamic noise. Aerodynamical noise levels emitted by different high-speed units depend on a number of design details which can significantly change emission values. High speed railway lines are increasingly spreading in modern countries where, simultaneously, environmental concerns about noise levels are also on the rise. Therefore, a practical methodology for assessing and comparing aerodynamic noise levels coming from high speed units has been declared as desirable both by international railway organizations such as UIC and national railway network managers. This article presents a quite simplified methodology capable of achieving a quantitative apportionment of noise coming from different directions in a high-speed railway pass-by.