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What To Do About Environmental Noise?
humans have shown that noise exposure, even at a moderate level, acts via an indirect pathway and has health outcomes that are similar to those caused by high noise exposures on the direct pathway (WHO, 2009). This is quite remarkable and suggests that even moderate exposure to environmen- tal noise levels is damaging to human health. Moreover, these biological responses to noise during sleep very often go unnoticed by human subjects (Basner and Samel, 2005) but nevertheless may be associated with the aforementioned health impacts.
As mentioned already, annoyance and sleep disturbance are the main impacts of excessive environmental noise exposure and they can lead to or be a trigger for more serious health problems resulting from environmental noise. These rela- tionships are now discussed.
The WHO (2009) concluded that one in three individuals in Europe is annoyed during the daytime while 57 million people (12% of the population) in 25 EU countries are an- noyed by road traffic noise; approximately 24 million (42%) of those are thought to be severely annoyed. Moreover, rail traffic noise is estimated to cause annoyance in about 5.5 million people (1% of the European population), 2 mil- lion of who are severely annoyed (den Boer and Schroten, 2007). Given the magnitude of the annoyance problem, it is perhaps a little surprising that the relevant authorities and policymakers have not been more active in attempting to alleviate the problems associated with environmental noise exposure (see Rochat and Reiter, 2016).
Noise annoyance is typically associated with the indirect reaction chain in humans that is closely related to the ini- tiation of emotional stress. Indeed, research studies have shown that individuals annoyed by noise tend to experience a series of negative emotions including anger, disappoint- ment, unhappiness, withdrawal, distraction, anxiety, ex- haustion, and even depression (WHO, 2011). However, un- derstanding the relationship between environmental noise exposure and annoyance is not a straightforward task. This is largely because the subjective discomfort resulting from environmental noise exposure in humans can be induced by individual perceptions of noisiness, disturbance to daily activities, or a broadly negative feeling about the surround- ing acoustic environment. One of the main characteristics affecting an individual’s perception of sound as noise is its loudness or perceived intensity (Stansfeld and Matheson, 2003). However, within existing scholarship, the evidence is mixed as to the importance of the duration and frequency 20 | Acoustics Today | Summer 2017
components of sound as well as the number of sound events involved in determining annoyance.
Despite this, nonacoustic factors such as age, socioeconomic characteristics, and fear of noise are thought to play a role in determining individual reactions to noise in the form of annoyance scores (Miedema and Vos, 1999, 2003; van Kamp et al., 2004). For example, after controlling for noise level, Fields (1992) found that noise annoyance increases with the fear of danger from the noise source, sensitivity to noise, the belief that the authorities can control the noise, awareness of the nonnoise impacts of the source, and the belief that the noise source is not important. Guaranoni et al. (2012) have suggested that only 33% of noise annoyance is accounted for by acoustic parameters. All off this outlines the importance of gaining a better understanding of human perceptions of environmental sound.
Road traffic noise is responsible for causing the greatest levels of annoyance (WHO, 2009). It has been shown repeatedly in attitudinal studies that the degree of noise annoyance depends on the mode of transport being considered (Miedema, 2004; Lam et al., 2009). At the same average noise level, the percent- age of individuals highly annoyed increases as one moves from rail traffic noise to road traffic noise to aircraft noise. This rela- tionship has led to the introduction of a rail bonus in legislation in some countries (e.g., Germany) where limit values for rail traffic noise is 5 dB(A) higher than other traffic modes because of its lesser impact on annoyance (Basner et al., 2011).
Sleep Disturbance
Sleep is an important modulator of hormonal release, glu- cose regulation, and cardiovascular function. Slow-wave sleep (SWS) is the restorative sleep stage. It is typically as- sociated with decreased heart rate, blood pressure, sym- pathetic nervous activity, and cerebral glucose utilization when compared with wakefulness (Halperin, 2014). It is during this stage that growth hormone is released and stress hormones are inhibited (Van Cauter et al., 2008). It is now well established in the literature that excessive environmen- tal noise disturbs sleep (WHO, 2011), notably in the form of arousals and awakenings and in reducing the amount of time an individual spends in the deep-sleep stages. These various forms of disturbance are related to health problems including hypertension, heart disease, and cognitive im- pairment in children (Murphy and King, 2014). Sleep dis- turbance can be quantified objectively by the number and duration of nocturnal awakenings, the number of sleep stage changes, and modifications in their amounts. Subjectively, it can also be measured through questionnaires distributed to

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