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What To Do About Environmental Noise?
respectively. Perhaps the most interesting results emerg- ing form the research was the revelation that rats do not habituate to their preexposure sleep pattern even after the exposure ends and that chronic exposure to an en- vironmental noise permanently disturbs sleep param- eters in rats. The research has potential insights for the relationship between environmental noise and sleep in humans.
The foregoing discussion notes that environmental noise is a significant health stressor that may lead to acute changes in blood pressure and heart rate as well as elevated levels of stress hormones in the body. As a re- sult, the evidence base linking environmental noise ex- posure and heart disease is increasing. In particular, the evidence demonstrating a link between transportation noise and ischemic heart disease (IHD) has increased considerably (Babisch, 2011, 2014). This is related to evidence that has emerged suggesting that noise exposure increases the risk of hypertension and arteriosclerosis (a thickening or hardening of the arteries). However, the evi- dence base is considerably stronger for the link with road traffic noise than for aircraft noise. Other studies have ex- amined the relationship between environmental noise and the prevalence of IHD that is generally assessed by cyclical symptoms of angina pectoris, myocardial infarction (MI), or electrocardiogram (ECG) abnormalities or from self-report- ed questionnaires regarding doctor-diagnosed heart attack (Babisch, 2006). The WHO (2009) has recently concluded that there is sufficient evidence to suggest a relationship be- tween excessive daytime noise exposure and increased car- diovascular risk. The most recent meta-analysis supports a relative 6% increase in IHD per 10-dB Lden increase in expo- sure to transportation noise (Vienneau et al., 2015).
Strategic Noise Mapping
The obvious question to emerge from such a review is, what to do about the problem of environmental noise? The policy and regulatory response to the problem has emerged primar- ily from Europe through the passing of Directive 2002/49/ EC, also known as the END. Article 7(1) of the END requires member states of the EU to produce strategic noise maps for all major roads, railways, airports, and agglomerations on a five-year basis, starting from June 30, 2007. It has resulted in the most comprehensive noise-mapping and population- exposure estimation process in the world.
A standardized schematic of the key steps involved in the strategic noise-mapping process is outlined in Figure 1. For 22 | Acoustics Today | Summer 2017
 Figure 1. Schematic of the noise-mapping process.
 the first phase (June 2007), strategic noise maps were com- piled for all agglomerations with more than 250,000 inhabit- ants; all major roads with more than 6 million vehicle pas- sages a year; railways with more than 60,000 train passages a year; and major airports with more than 50,000 movements a year within the territories. The results of this process have recently been made available via a noise observation and in- formation service for Europe (NOISE) that is maintained by the European Environment Agency (EAA; see http://noise. A number of scholars undertook an analysis of the finding of the results of the first phase (see van den Berg and Licitra, 2009; Murphy and King, 2014) and outlined significant methodological issues relating to the comparability of results across member states (Murphy and King, 2010). The second phase (June 2012) required that strategic noise maps were produced for all agglomerations with a population in excess of 100,000 individuals and also saw a reduction in the thresholds for major roads (to 3 mil- lion vehicle passages) and railways (to 30,000 vehicle passag- es). The strategic maps must satisfy minimum requirements as listed in Annex IV of the END and should be reviewed every five years.
In the END, noise mapping is defined as the presentation of data on an existing or predicted noise situation in terms of a noise indicator, noting breaches of any relevant limit value in force, the number of people affected in a certain area, or the number of dwellings exposed to certain values of a noise indicator. From this, it can be seen that under the END, noise maps are considered to be multidimensional be- cause they incorporate not only measured/calculated noise levels for a geographic area but also include information

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