Abstract
Environmental noise can be defined as the accumulation of noise pollution caused by sounds generated by outdoor human activities, Road Traffic Noise (RTN) being the main source in urban and suburban areas. To address the negative effects of environmental noise on public health, the European Environmental Noise Directive requires EU member states to tailor noise maps and define the corresponding action plans every five years for major agglomerations and key infrastructures. Noise maps have been hitherto created from expert-based measurements, after cleaning the recorded acoustic data of undesired acoustic events, or Anomalous Noise Events (ANEs). In recent years, Wireless Acoustic Sensor Networks (WASNs) have become an alternative. However, most of the proposals focus on measuring global noise levels without taking into account the presence of ANEs. The LIFE DYNAMAP project has developed a WASN-based dynamic noise mapping system to analyze the acoustic impact of road infrastructures in real time based solely on RTN levels. After studying the bias caused by individual ANEs on the computation of the A-weighted equivalent noise levels through an expert-based dataset obtained before installing the sensor networks, this work evaluates the aggregate impact of the ANEs on the RTN measurements in a real-operation environment. To that effect, 304 h and 20 min of labeled acoustic data collected through the two WASNs deployed in both pilot areas have been analyzed, computing the individual and aggregate impacts of ANEs for each sensor location and impact range (low, medium and high) for a 5 min integration time. The study shows the regular occurrence of ANEs when monitoring RTN levels in both acoustic environments, which are especially common in the urban area. Moreover, the results reveal that the aggregate contribution of low- and medium-impact ANEs can become as critical as the presence of high-impact individual ANEs, thus highlighting the importance of their automatic removal to obtain reliable WASN-based RTN maps in real-operation environments.
Highlights
Environmental noise can be defined as the accumulation of noise pollution caused by sounds generated by human activity outdoors, mainly produced by transport, road traffic, rail traffic, air traffic and industrial activities [1]
After the deployment of the two Wireless Acoustic Sensor Networks (WASNs) in the urban and suburban pilot areas, this paper evaluates the aggregate impact of Anomalous Noise Events (ANEs) on the L Aeq computation of Road Traffic Noise (RTN) in both environments in real operation
ANEs from each sensor location bias the L Aeq,300s measurement, the impacts are categorized within three impact ranges (i.e., NR = 3) [37], accounting for those occurrences causing a low-impact in θ1 = (−∞, 0.5) dB, a medium-impact in θ2 = [0.5, 2) dB, and, a high-impact in θ3 = [2, +∞) dB, θ3 = θc being as this last interval collects those cases that surpass the critical threshold γc = 2 dB according to the Working Group Assessment of Exposure to Noise (WG-AEN) [14]
Summary
Environmental noise can be defined as the accumulation of noise pollution caused by sounds generated by human activity outdoors, mainly produced by transport, road traffic, rail traffic, air traffic and industrial activities [1]. According to the World Health Organization, noise exposure produces a loss of around one million healthy life years in Western Europe every year due to different types of derived diseases [2,3]. Focusing on this public health problem, the European (EU) authorities published the Environmental Noise Directive (END) [1] in 2002, which requires the EU member states to tailor noise maps and to develop the subsequent action plans to mitigate noise every five years for Sensors 2020, 20, 609; doi:10.3390/s20030609 www.mdpi.com/journal/sensors. This premise was further endorsed by [7,8], which led to the development of an updated version of the CNOSSOS-EU [9]
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