Urban Noise Pollution: Sources, Effects, and Solutions
Urban noise has been declared a pollutant by the World Health Organization (WHO) since 1972. Over the last decades, the quality of the urban environment has attracted the interest of researchers due to the growing urban sprawl, especially in developing countries. Urban noise can be considered one of the main sources of pollution. Nowadays, acoustical environmental quality in urban areas is threatened.
The urban environment is composed of several audible sources. Traffic (road, rail, and air), industrial facilities, civil construction and social activities (parties, fairs and open air markets, and residential noise) all contribute to the conversion of the soundscape in noise pollution. Noise pollution can be considered one of the main agents of loss of environmental and life quality in a metropolis and its dissemination pushed the boundaries of industrial facilities, spreading through the streets and also for leisure activities, moments of rest and work.
This article aims to evaluate the effects of noise exposure in urban soundscapes, focusing on the sources, health impacts, and potential solutions to mitigate this pervasive environmental issue.
Understanding Soundscape and Noise Measurement
Schafer introduced the concept of soundscape as a scope to thinking beyond the noise levels, considering human experience in the environment and its cultural dimension. Soundscape research means to focus on the meaning of sounds and its implicit assessments, and understanding perceptual effects.
Because noise is measured using a logarithmic scale, a 3 dB(A) change in noise, a level which is generally noticeable, corresponds to a doubling in the power of the generated noise. Measures of noise exposure integrate sound power over a period of time. The instantaneous maximum or peak values Lmax is a measure used for equipment regulation but not typically used as a measure of human exposure.
Noise maps are descriptors of external environmental noise, expressed by means of indicators, which are determined by reference periods and represented by lines that indicate the identical rating levels (isophone lines) and limit the areas to which a specific class of values expressed in decibels (dB[A]) corresponds.
Urban soundscape - Leisure - Selected route and their noise map in exposed area: Quinta do Covelo.
Sources of Urban Noise
Cities have many sources of noise; many of the more significant and preventable sources arise from traffic and industry. The urban environment is composed of several audible sources: Traffic (road, rail, and air), industrial facilities, civil construction and social activities (parties, fairs and open air markets, and residential noise).
For example, almost all aircraft in current operation must meet standards for runway takeoffs, landings, and sidelines, which depend on the aircraft's weight and its number of engines. However, noise may substantially increase for residents living near a newly planned airport. Furthermore, emissions standards do not address the problem of cumulative emissions.
Health Effects of Noise Pollution
Chronic exposure to elevated levels of community noise creates significant health risks. The effects of exposure to noise on the human organism are subject to the specific characteristics of the noise, such as frequency, intensity, and exposure time, and also individual susceptibility. These health impacts of noise depend on the intensity of noise, on the duration of exposure, and the context of exposure.
Noise is a biological stressor; it triggers autonomic chemical mechanisms for arousal and alertness.
Impact on Sleep
Noise interferes with sleep. Noise can make it difficult to fall asleep, and abrupt noises can cause awakenings, which the sleeper may not sense or recall. Even at levels below which awakening may occur, noise produces measurable physiological reactions, such as increase in heart rate and body movements and can cause disturbances of natural sleep patterns by causing shifts from deep to lighter stages.
Sleep disturbance can begin at relatively modest noise levels (40 dB). At the level of noise produced by a busy road, the proportion affected by sleep disturbance becomes significant. Average nighttime noise level of 65 dB will result in self-reported disturbance of sleep in about 15% percent of the population.
Mitigation and Solutions
Thoughtful planning and building rules and their strict enforcement can mitigate many noise conflicts. Zoning codes can limit the incompatible proximal location of residential and commercial uses. Enforcement of all noise laws is variable and often subjective.
At the national level, regulations limit the allowable sound levels produces by aircraft, railway and roadway vehicles and certain heavy equipment. Municipalities can purchase quieter public service and transit vehicles (e.g. electric and hybrid buses). Cities can adopt building standards to require quiet interiors (e.g. Subsidize acoustical retrofits (e.g.
In 2002, the European Union adopted the Directive 2002/49/CE20[8] regarding the assessment and management of environmental noise, with the goal of controlling and reducing sound pollution using a common approach and avoiding or preventing the harmful effects of noise exposure. The EU established the enforcement of developing strategic noise maps that should estimate the exposure to outside ambient noise, based on assessment methods in agreement to the EU levels.
Case Study: Porto, Portugal
A study was conducted in the city of Porto, Portugal, to evaluate the effects of noise exposure in different urban scenarios. The study was conducted in two steps: Evaluation of noise levels, with the development of noise maps, and health related inquiries. 180 individuals were interviewed, being 60 in each scenario, divided into 30 exposed to high level of noise and 30 to low level.
Two areas representative of the exposure categories were selected within each scenario. Areas influenced by traffic noise were chosen to represent the exposed areas and areas with little influence from traffic noise were selected for the non-exposed areas. The development of the noise maps was based on the allocation classification criteria for each area. Areas that are allocated for residential use, as well as schools, hospitals, and public leisure areas were classified as sensitive zones.
The energetic averages calculated in each scenario also allow the inference that the areas chosen to be representative of the exposed areas have exceeded the legal limits while the non-exposed areas had values below these limits.
Findings from the Porto Study
70% of the interviewees reported noticing some source of noise in the selected scenarios and it was observed an association between exposure and perception of some source of noise. 41.7% of the interviewees reported some degree of annoyance, being that this was associated with exposure. There was also an association between exposure in different scenarios and reports of poor quality of sleep.
It was observed that in the work scenario the chance of reporting significant annoyance was tripled when compared with the leisure scenario, while in the home scenario, this chance was the quadruple of that of the leisure scenario.
The majority of the interviewees considered noise as an environmental problem (88%) and believed that noise exposure can cause or aggravate health conditions.
Table: Exposure Areas and Energetic Average in Urban Soundscapes
| Urban Soundscape | Exposure Area | Energetic Average |
|---|---|---|
| Leisure | Quinta do Covelo (Exposed) | Exceeded Legal Limits |
| Leisure | Parque da Cidade (Non-Exposed) | Below Legal Limits |
| Work | 31 de Janeiro St., Passos Manuel St., and Sá da Bandeira St. (Exposed) | Exceeded Legal Limits |
| Work | Santa Catarina St. (Non-Exposed) | Below Legal Limits |
| Home | Outeiro neighborhood (Exposed) | Exceeded Legal Limits |
| Home | Carriçal neighborhood (Non-Exposed) | Below Legal Limits |