Analysis of increased annoyance reactions after the introduction of new tramways, based on psychoacoustic parameters

The introduction of new tramway types in the city of Graz (Austria) resulted in strong complaints from residents in certain areas. To better understand the underlying reasons, a systematic measurement campaign was designed for 6 locations in Graz and 2 locations in a comparable European city. This procedure combined measurements for vibrations and sound, which were conducted from 8pm to 8am at each location. Measured vibration levels (Wm weighted) remained below the limits of the applicable standard. A systematic difference between "old" and "new" tramways was not detectable with standard vibration or acoustic indicators. However, a strong underestimation of the acoustic feature by A-weighting (C-A > 20 dB) was observed. The signal-to-noise-ratio based on C-weighted levels clearly distinguished "old" from "new" trams. Further analysis of the psychoacoustic parameters revealed only marginal differences in loudness and tonality. Roughness was associated with higher values for "new" trams at some locations. However, the "new" trams exhibited higher values for sharpness, but mainly at higher speeds. The high variance of vibration and sound indicators at the various locations makes it difficult to identify a single main determinant. Rather the integrated consideration of the various indicators enables a proper assessment to implement appropriate technical solutions.