Analysis of psychoacoustic and vibration-related parameters to track the reasons for health complaints after the introduction of new tramways

Abstract

Background: A change to new tramways in Graz (Austria) led to severe complaints in residential areas. To understand the underlying reasons for these complaints, a systematic measurement campaign was designed. Methods: Six locations in Graz and two locations in a comparably sized city were selected. Parallel indoor recordings of sound and vibrations were conducted from 8:00 p.m. to 8:00 a.m. (due to sleep problems) at all locations. Results: Vibration levels remained below the limits of the Austrian standard (Wm-weighting) although variability was observed among sites, tram types and pass-bys. A complex characteristic of the acoustic feature space was found with A-weighting (differences between A- and C-weighting of more than 15 dB were observed). C-weighted background to peak noise ratios clearly distinguished "old" from "new" trams. Psychoacoustic indices indicated a high variability between locations and tram types. Roughness and loudness was higher in "new" versus "old" trams at most locations. "New" trams exhibited high sharpness values and variability, especially at higher speeds-when compared with trams from a control city. Conclusions: Standard indicators of sound and vibration were not sensitive enough to uncover the reasons for the complaints. Only the integrated analysis of the ambient soundscape (high signal-to-noise-ratio), the more noticeable sound (in psychoacoustic terms) and the observed high variance of the immissions provided guidance to implement appropriate technical solutions.