Squealing noise in light rail transport systems: Implications in noise mapping

Squealing noise is generated by railway vehicles riding through curves having closed radius. It is a result of wheels sliding on the rail when they negotiate a curve. This kind of noise is very annoying for people living in the surrounding areas where this phenomenon occurs because it has a characteristic spectrum that is dominated by discrete frequency components. Usually, squeal noise is not correctly accounted in urban areas noise maps. This paper presents the results of field measurements of squealing noise in Porto (Portugal) where a new light-rail system is operating. The goal was to characterize the acoustic effect of this type of noise in making noise maps. With the results obtained from in situ measurements, the squealing noise was simulated using Cadna/A software. This paper compares three variants of squeal noise use and simulation with the software CADNA/A. Comparing the noise map generated using the field measurements, with maps taking no account for squealing noise, a large difference in noise levels can be found (up to 17 dBA) leading to errors up to 100 m in noise exposed areas. A correction method was found to be easily incorporated in this model to improve the noise map estimation procedure.