Assessing noise pollution in sensitive areas: Soundscape analysis in an alpine valley by psychoacoustic means

Abstract

Alpine valleys are sensitive areas due to topography, meteorology, housing, and land-use pattern, that modify noise propagation and make protection against noise pollution rather difficult. The ‘‘amphitheater’’ effect was mentioned as explanation for deviating noise-annoyance curves and health effects observed at lower sound levels. However, detailed empirical analyses are lacking. In this study a series of simultaneous, binaural sound recordings was carried out in several cross sections of the Wipp Valley along the central-European transportation route to the Brenner pass. During 6 weeks a wide variety of day- and week times was sampled with variable wind (‘‘Foehn’’) and weather conditions (dry, rain, snow). Sound recordings were paralleled by meteorological recordings near the source and on the slope. First analyses have revealed several facts. (1) The assumption of linear sound propagation to the slope is seriously in error. (2) Tonal components from gearboxes are a significant feature in the slope recordings. (3) Low-frequency modulations make the sound more intrusive on the slope—while near the source this feature is better masked. (4) Low background sound levels (<30 dB,A) on the slopes are in sharp contrast with incoming sound levels (52 dB,A,Leq about 1200 m from the source). (5) Meteorology leads to substantial changes in measured sound levels.

Prediction of psychoacoustic parameters

“…However, the total of perceived annoyance depends on the location of the two sound sources relative to the listener. On the other hand, it is possible for an existing sound source of high annoyance to be masked by a second sound source of preferred sound quality 6 . For example, the subjective perceived impulsiveness of individual sound sources can be reduced by adding noise of a comfortable sound quality 7 .…”

The Software Prediction of Psychoacoustics Parameters

“…For example, the subjective perceived impulsiveness of individual sound sources can be reduced by adding noise of a comfortable sound quality. [8], [13] It is needed a mapping with psychoacoustic parameters to predict adequately the sound quality or the annoyance at different places. While it is possible to precisely predict A-weighted sound pressure related to the distance from the noise, such methods of calculation are not applicable for psychoacoustic parameters such as loudness, and particularly sharpness, roughness, and fluctuation strength because they are non linear and the influence of distance is not simple predictable.…”