Managing noise levels in passenger carriages
Sound levels within passenger carriages influence the quality of the passenger experience. While the process of measurement of passenger noise levels on trains is standardised, there is no legislation or standard that mandates limits on the sound levels.
The Key Train Requirements (KTR), owned by the Rail Delivery Group and RSSB, provides guidance for the specification of new rolling stock, and has been recently extended to include additional guidance on internal noise. However, there was little evidence on which to base these values and little understanding as to how these noise levels impact passenger comfort.
RSSB commissioned the Acoustics group at the University of Salford to determine appropriate targets and metrics to be recommended in future versions of the KTR.
The study reviewed existing noise assessment methods, standards and legislation, noise levels across different modes of transportation, and noise levels across a limited number of passenger rolling stock.
Finding that on-train data was limited in availability, the research focused on a qualitative analysis of the noise levels in rail passenger carriages. This included considering how noise affects passenger comfort levels, and how passenger perception of noise can be improved by specifying noise quality parameters in industry guidance.
Based on the data available, the study concluded that the current KTR target noise limits can be considered an achievable upper boundary. In addition, sound levels found in mainline train passenger carriages (excepting metro services) appears to be below those found in planes or buses.
The study highlights the importance of the use of sound quality metrics (SQMs) in providing a better prediction of passenger comfort. It has made recommendations for how these may be incorporated into the KTR in future.
Providing the railway industry with a common understanding of the effects of noise levels and sound quality on passenger comfort can ultimately be used, through procurement and specification, to drive improvements for passengers.