Effects of road traffic noise and the benefit of access to quietness

https://doi.org/10.1016/j.jsv.2005.11.034Get rights and content

Abstract

Socio–acoustic surveys were carried out as part of the Soundscape Support to Health research programme to assess the health effects of various soundscapes in residential areas. The study was designed to test whether having access to a quiet side of one's dwelling enhances opportunities for relaxation and reduces noise annoyance and other adverse health effects related to noise. The dwellings chosen were exposed to sound levels from road traffic ranging from about LAeq,24h=4568dB at the most-exposed side. The study involved 956 individuals aged 18–75 years. The results demonstrate that access to quiet indoor and outdoor sections of one's dwelling supports health; it produces a lower degree and extent of annoyance and disturbed daytime relaxation, improves sleep and contributes to physiological and psychological well-being. Having access to a quiet side of one's dwelling reduces disturbances by an average of 30–50% for the various critical effects, and corresponds to a reduction in sound levels of (LAeq,24h) 5 dB at the most-exposed side. To protect most people (80%) from annoyance and other adverse effects, sound levels from road traffic should not exceed (LAeq,24h) 60 dB at the most-exposed side, even if there is access to a quiet side of one's dwelling (LAeq,24h⩽45 dB).

Introduction

Environmental noise is recognized as a major health problem. The adverse health effects (i.e. general annoyance, speech interference, and sleep disturbances) of transportation noise are well documented [1]. Unlike many other environmental problems, noise pollution is still worsening. Thus, since 1992 it is the only environmental impact in Europe about which public complaints have increased [2]. In Sweden, the number of persons exposed to traffic noise exceeding outdoor guidelines (LAeq,24h=55dB and LAmax=70dB) is approximately 2 million or 25% of the population. In 1998, 840 000 people were estimated to have been exposed in their dwellings to road, air, and railway traffic noise exceeding indoor guidelines (LAeq,24h=30dB and LAmax,22-06=45dB) [3]. Nearly one million adults, or 22% of the Swedish population, are disturbed by noise in their homes; traffic and neighbours are the noise sources that annoy most people [4]. In residential areas, road traffic is normally the dominant noise source, and estimates show that road traffic will grow by 29% from 1997 to 2010 for personal transport [5] and by 25% for freight transport [6]. This increase is unsustainable and strategic action is required to reduce the adverse effects of such environmental noise. The Swedish government [7] has formulated long-term goals for the sustainable development of the built environment. One goal for 2020 is that no one should be exposed to sound levels above the indoor and outdoor guidelines. A wide gap prevails, however, between the existing noise environment and the long-term goals formulated by authorities in European countries. Development of methods to reduce noise at source (new road surfaces, etc.) will be inadequate to reverse the present negative trend. Recent studies show that over the past 25 years, noise emissions from individual road vehicles in normal traffic have decreased only by 1–2 dB (e.g. Ref. [8]). A new approach is needed if an acceptable noise environment is to be achieved in a reasonable time frame. Such an approach must be supported by scientific evidence.

Section snippets

Background and research strategies

The Swedish multi-disciplinary research programme Soundscape Support to Health has formulated a strategy for improving sound environments in residential areas. This strategy supports personal health and well-being and could potentially reverse the trend toward increasing adverse health effects of noise in residential areas. The programme aims to combine methods to abate emissions from noise sources (primarily road traffic) with optimal soundscape design. The intention is to create supportive,

Aim of the studies on adverse health effects

The scientific aim of the health and well-being studies in the research programme was to explore how various adverse health effects, behaviours, and self-estimated noise sensitivity relate to individual acoustic and perceived soundscapes (including when subjects have access to a quiet side in their dwellings). Within the programme three projects have been conducted to assess health effects of soundscapes: (i) cross-sectional, (ii) longitudinal, and (iii) experimental/quasi-experimental studies

Overall design of empirical studies on adverse health effects

Adverse health effects were empirically examined in cross-sectional field studies conducted in carefully selected residential areas during a 3-year period (2000–2002). Health and well-being effects were assessed using questionnaires (accompanied with an introductory letter) sent to the selected population samples. Sound levels from road traffic were then assessed by calculations and measurements. Data from 956 individuals regarding various health effects were linked to data regarding individual

General annoyance in relation to sound levels and access to a quieter side of the dwelling

The main aim was to determine whether access to a shielded, quieter side of a dwelling has a positive effect on noise annoyance. The results clearly demonstrate the health benefits of having such access. Fig. 2 shows general annoyance assessed using the 5-point category scale (“not at all” to “extremely annoyed”) as the percentage of subjects moderately, very, and extremely annoyed at various sound level categories and in relation to type of dwelling. The number of individuals at sound levels

Method

To clarify the relationship between acoustic soundscapes including the importance of having access to a quiet side of one's dwelling for various adverse health effects, we selected study sites carefully. The intention was to select one set of five study sites with sound levels (LAeq,24h) ranging from 45 to 65 dB at both sides (road and courtyard sides) and another set of five study sites with these same sound levels at the most-exposed side (road side) but with approximately 10–20 dB lower sound

Conclusions

A very good sound environment that promotes health and well-being is one where sound levels from road traffic noise in residential areas are below LAeq,24h=45dB, free field value. Access to quiet indoor and outdoor sections of one's dwelling supports health and results in a lower degree and extent of annoyance, disturbed relaxation and sleep, and contributes to physiological and psychological well-being. The benefit of having access to a quiet side of one's dwelling averages 30–50% for

Acknowledgements

This paper is based on research performed as part of the programme Soundscape Support to Health, sponsored by the Swedish Foundation for Strategic Environmental Research (MISTRA), the Swedish Agency for Innovation Systems (Vinnova), and the Swedish National Road Administration (VV).

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