Proposals for improved measurement methods for curve squeal and braking noise

Abstract

Improved methods for measuring curve squeal and braking noise have been proposed within the ACOUTRAIN project, intended as input to future standards. In this paper an outline of these methods is given and the underlying considerations are explained. The EU TSI regulation limiting noise emission of new rail vehicles does not yet specify limits for curve squeal or braking noise, which are both relevant noise sources but not easy to characterise reliably due to their variability. No ISO or EN standard exists for curve squeal. Braking noise is included in the current EN ISO 3095 noise type testing standard, but the procedure requires improvement in relation to measured quantities. For curve squeal, two methods are proposed, an occurrence test using on board measurements along a route with various curves, and a trackside test for curves or switches. The existing UIC trackside test is taken as basis using the percentage exceedance indicator L10. For braking noise, improvements to the existing trackside measurement standard are proposed, taking the variety of potential noise sources and their variable position and operating condition into account. The measurement quantity, positioning and braking operation are the main topics. Without proposing limit values, some considerations are put forward that may be taken into account when applying the methods for compliance testing for curve squeal and braking noise.