Railroad and rail transit noise sources

Abstract

The railroad or rail transit system design team must predict A-weighted, or preferably, octave band sound pressure levels near passing trains. This is the first step in estimating noise over any area of potential impact and in subsequent selection among noise abatement design alternatives. In this paper recently reported measurements of locomotive and railcar noise emission are reviewed and presented for use in making such design predictions. Locomotive noise is largely confined to the range of 75 to 95 dB(A) at 30 m (100 ft) for all speeds. For various railcars on tie and stone ballast track the trend of data suggest that A-weighted sound levels increase uniformly with speed over the speed range of available data, now reaching 400 km/h (250 mile/h). At a given speed these data typically have a noise level range of 15 dB. The data show an apparent lower bound for noise among steel wheel on steel rail vehicles operating today. Octave band spectra are given relative to A-levels for various locomotive and railcar types. These recent data disagree with some average spectra based on data from 1970 and earlier. Reported measurements and estimates of noise level reductions from various locomotive, railcar and track design factors are tabulated; the data exhibit considerable scatter. Two current procedures in which the above-mentioned data are used to predict pass-by noise levels and spectra are described and evaluated. It is concluded that for estimating noise level reduction due to combinations of treatments, or for estimating octave band reduction, procedures and useful data are limited. To provide more precise design information future experiments must take better account, either deterministically or statistically, of all factors which influence measured noise, including some discussed herein which cannot always be controlled by test team or design team decisions.