Assessing Environmental Impact of Transport Noise with Wireless Sensor Networks

One of the problems associated with assessing the impact of noise pollution is the relative nature of sound measurement. Apart from the fact that sound levels are measured on a logarithmic scale, noise intrusion can often be highly relative to the listener’s surroundings. The impact of noise events is commonly compared with the background or ambient noise level and so is not solely dependent on the decibel level of the noise. As a result, it is difficult to quantify the personal or environmental impact of particular noise levels. A number of approaches have been adopted over the years that aim to put a value on noise reduction, either by gauging the annoyance to the public or by estimating the economic value of noise abatement. A recent study by a European Union (EU) working group of noise experts suggests a method based on dose–effect relationships for evaluating the number of people annoyed by noise from a given source (2). The dose–effect relationship is the relationship between the dose of harmful factors (i.e., noise) and the severity of their effect on exposed subjects. This position paper (essentially an advisory paper for the European Council) uses the percentage of people annoyed (%A) and percentage of people highly annoyed (%HA) as metrics for noiserelated annoyance in a community. The noise indicator used is Lden, as selected for noise annoyance in the EU noise directive (3). Lden is a noise-level reading that takes account of day, evening, and nighttime noise. Weightings are applied to the different periods to account for the fact that noise can be more annoying at different times of the day. The evening period (7:00 to 11:00 p.m.) carries a weighting of +5 dB, and nighttime noise (11:00 p.m. to 7:00 a.m.) carries a penalty of +10 dB. The Lden represents the yearly average noise level. The use of dose–effect relationships produces results that are more comprehensible for the general public; not everyone is familiar with the Lden measurement but a useful measure of how annoying a particular noise source is can be easily understood. The working group proposed expressions for estimating the %A and %HA for a given source of transportation noise. The position paper also outlines possible mitigation strategies that may arise from the calculation of Assessing Environmental Impact of Transport Noise with Wireless Sensor Networks