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.
Highlights
The demand for public transport is increasing continuously, for large, and for medium and smaller sized cities in order to mitigate congestion and provide flexible mobility
The current scientific data base regarding tramway immissions is small, most reported sound levels only in dBA, neglecting potential low frequency components and other specific characteristics of tramway sounds, which are produced by the various noise sources of this complex vehicle [7]
Measured vibrations were analyzed based on Wm-weighted acceleration with time
Summary
The demand for public transport is increasing continuously, for large, and for medium and smaller sized cities in order to mitigate congestion and provide flexible mobility. Potential adverse health effects of noise and especially vibrations are rarely discussed, while effects of air pollution and related climate issues are the central themes [4]. The current scientific data base regarding tramway immissions is small, most (except [11,12,13]) reported sound levels only in dBA, neglecting potential low frequency components and other specific characteristics of tramway sounds, which are produced by the various noise sources of this complex vehicle [7]. Results: Vibration levels remained below the limits of the Austrian standard (Wm-weighting) variability was observed among sites, tram types and pass-bys. C-weighted background to peak noise ratios clearly distinguished “old” from “new” trams. Atatlower differencein inthe thesound soundpressure pressurelevels levels noticeable points to the importance of these frequency for assessing the annoyance sleep points to the importance of these frequency spectraspectra for assessing the annoyance and sleepand interference interference the studied tramways
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