This paper deals with field observations of curving noise from revenue service trains on a mainline corridor. A specific trackside measurement methodology has been designed to verify the influences of the main parameters: wheel angle of attack, vertical and lateral rail forces, wheel lateral position, train speed and weather conditions. This paper focuses on the role of the wheel angle of attack on curving noise generation. A detailed method of curving noise identification, including the type of curving noise and its generating wheel, is presented. It is observed that all severe squeal noise events (>100dBA) were generated from high wheel angle of attack (>10mrad), while flanging noise has no obvious relationship with wheel angle of attack. A surprising finding from this measurement exercise is that squeal noise was generated from the outer wheel/high-rail interface, which is contradictory to the conventional knowledge. © 2012 Springer.