A Case Study of Railway Curving Noise Accounting for Squeal Generated from Both the Outer and Inner Wheel

Abstract

A comprehensive case study of curve squeal in a 213 m radius curve on the Stockholm metro is presented. It includes measurements of track characteristics (rail profile, rail roughness and gauge width) and noise measured at the trackside as well as by two vehicles equipped with an on-board mounted noise monitoring system. The current case study contrasts field measurements of curve squeal reported in the literature by a relative shift of emitted noise towards higher frequencies. Wayside noise measurements in the studied curve showed squeal generation for all vehicle passages with dominating 1/3 octave band centre frequencies in the range between 6.3-15.8 kHz. Noise data measured during one year of regular traffic of two vehicles equipped with a monitoring system were obtained. The occurrence of curve squeal was analysed through an implementation of the curve squeal detection algorithm in operation at the Stockholm metro. This algorithm was also applied to search for events of squeal noise radiation from the outer wheel. Results show emissions of squeal noise from the inner and outer wheel for 65% and 8% of the vehicle passages through the studied curve, respectively. Further, the occurrence of curve squeal radiated from the inner wheel was found to increase by 10% after rail grinding. In the literature, squeal radiated from the outer wheel is described as having an intermittent character with magnified spectral components in the frequency range between 5-10 kHz. In contrast, the current work presents sustained tonal squeal generated from the outer wheel with similar noise characteristics as typically related to ordinary curve squeal.

Keywords: Curve squeal, flange squeal, noise monitoring, rail grinding, rail roughness, rail profiles