Environmental noise is one of the major environmental risks to human health, with road traffic noise being the most common source of community noise in urban areas. Population exposure to excessive noise levels has cumulative adverse effects also on well-being. Thus, there is an urgent need to assess and manage environmental noise, with a focus on road traffic noise (RTN).
Research on RTN has been unfolding for many years and has many fronts. While the knowledge of this subject has already enabled the implementation of effective road traffic noise interventions across Europe, there is still room for advancement. This includes gaps in the understanding of socioacoustic aspects of RTN interventions or, even in a more fundamental perspective, the parameters affecting tyre/road noise generation.
This PhD research aims to explore noise perception by shifting the focus of analysing RTN with the actual noise levels to understand the causal relations between objective noise, the perception of noise by exposed people and potential adverse health effects. The main work packages are described as follows.
- Low-noise thin asphalt layers (TALs) and noise barriers are road traffic-noise mitigation measures. TALs are applied in urban environments, while noise barriers are more often used to shield residents in the vicinity of highways or national roads. Two TALs experimental sites and three noise barrier sites were investigated. The objective noise level reductions were measured via noise modelling and acoustic measurements. Subjectively, longitudinal socio-acoustic surveys assessed residents’ perceptions, especially regarding noise annoyance.
- Another work package involves road traffic noise measurements, mainly the Statistical Pass-By method (SPB). Temperate is a cause of variation in tyre/road noise measurements. For this reason, noise levels have to be corrected to a reference temperature. A large SPB measurement campaign was conducted with a focus on heavy traffic to create temperature correction coefficients. We further analysed the recordings from this measurement campaign to explore the psychoacoustic indicators for various vehicle classes.
- While the distribution of sound sources in space and time gives rise to the acoustic environment, the soundscape is a person’s perception of the acoustic environment, within a specific context [2]. In this work package, a large soundscape survey in Flanders was carried out via the citizen science project ‘De Oorzaak’. This data was linked to information from open geographic databases to describe how participants’ surroundings affect soundscape assessment, for example, population density, degree of urbanisation, green areas, etc.
- A final work package includes a listening test with a visual component using virtual reality. A Close ProXimity (CPX) measurement campaign was conducted to record tyre/road noise of several road surfaces at different driving speeds. These noise signals were then binaurally auralized to resemble a car pass-by noise. For the visual component, a virtual reality environment resembling an urban setting was created, with three degrees of greenery (none, medium, high). This experiment aims to measure how do subjects react to these three variables in terms of noise annoyance and physiological responses (skin conductance and heart rate).