A novel method for optimizing in-car rolling noise levels within a railway tunnel environment

Abstract

In-car noise levels within trains rolling on surface track are usually controlled by noise and vibration which is generated at the wheel–rail interface and then transmitted through the chassis and floor of the train cabin. In a railway tunnel environment, higher noises levels result from the build up of reverberant noise, and if left untreated this increased noise can affect passenger comfort and make it harder to listen or converse. In extreme cases, it can lead to adverse health effects: travellers may complain and avoid using the rail service as a result. Accordingly, the acoustic design of railway tunnel environments generally includes consideration of various treatments to reduce noise ingress into vehicle interiors, particularly given treatments to the vehicles themselves may not be cost effective. Modeling of in-car noise levels within tunnels has traditionally used the Sabine equation as part of the design process. Because the Sabine equation was never intended for this application given the geometry and frequencies involved, an improved method which recognized the near field effects was developed in order to provide confidence in the acoustic design. In this presentation, this novel method for modeling in-car rolling noise levels and optimizing sound absorptive treatments within a tunnel is discussed. Modeling results and measurements from a recent major rail project are used to demonstrate the effectiveness and improvements in outcomes from traditional approaches.