Importance of Noise-Spectrum Measurements for Noise Control in Railway Vehicles

Abstract

The authors have been working on noise control in railroad cars and engines. The key problem is the loudness evaluation of the typical broad-band railway noise with sufficient accuracy. However, it was found that the absolute value of the loudness level is of less importance than the difference between two noises—e.g., any improvement caused by some sort of acoustical adaptation, the increase of loudness level owing to higher moving speeds, the separation of the noise into single components, etc. For this purpose, direct measurements with the sound-level meter are simple, but so crude that sometimes they even contradict the subjective impression of loudness. Loudness calculations based on spectrum data give much better results. Results of loudness measurements and calculations for typical railroad noises are given. The differences between some of the usual loudness measures are outlined, and some conclusions with regard to noise control are discussed.