Living in a rural landscape in contrast with an urbanised area enhanced the risk of perceiving wind turbine noise and, furthermore, the risk of annoyance. Type of terrain had no major influence on perception in urbanised areas; however, in a rural landscape, complex terrain substantively increased the risk. These results suggest, together with the higher risk of perception in areas rated as quiet, that there is a need to take the special features of an environment into account when assessing the risk of nuisance for people living in the area.
The findings of our study could in part be explained by differences in levels of background sound between rural and urbanised areas. However, not just perception but also annoyance was associated with type of landscape, indicating that the wind turbine noise interfered with personal expectations in a less urbanised area. Having renovated the dwelling was another variable that was positively associated with annoyance, pointing towards a personal factor related to the living environment, which affects response to an environmental stressor. Theories used in studies of residential environments have revealed that people choose environments that harmonise with their self‐concept and needs, and that they remain in places that provide a sense of continuity.16
When a new environmental stressor occurs, the individual's relationship with her or his place of residence is disrupted.17
Such a distortion could possibly predispose for an increased risk of annoyance such as measured in our study.
The increased risk of perception of wind turbine noise in a rural landscape with a complex terrain compared with a flat terrain could be due to shelter effects decreasing the background noise at the respondent's dwelling, where the houses are located in a valley and the turbine on a hill. Also, it cannot be excluded that the model used for calculating the sound propagation underestimates the A‐weighted SPL at the respondent's dwelling more than compensated for in this study, in cases where there are large differences in altitude between the source and the receiver.9
The association between perception of wind turbine noise and A‐weighted SPL was statistically significant and consistent (OR 1.3) even when several moderating variables were tested. The association between noise annoyance and sound level (OR 1.1) was also consistent for most moderating variables, even though it was not always statistically significant, largely owing to the low number of annoyed persons. However, when the vertical visual angle was tried in a logistic regression, the association between annoyance and sound decreased (OR 1.0). Both A‐weighted SPL and vertical visual angle were calculated from the distance between the respondent and the wind turbine, so the decrease may be due to the dependence of the variables. The decrease could also be seen as an indication of the visual influence that wind turbines have on noise annoyance. Seeing one or more turbines increased not just the odds of perceiving the sound, but also the odds of being annoyed, suggesting a multimodal effect of the audible and visual exposure from the same source leading to an enhancement of the negative appraisal of the noise by the visual stimuli. This effect has previously been observed in a field study where traffic noise was found to be more annoying if the source of the noise (moving road traffic) could be seen.18
On the other hand, the increased odds of being annoyed, observed among respondents with a negative attitude to the wind turbine's visual impact on the landscape, point to a more aesthetic explanation: respondents who think of wind turbines as ugly are more likely to appraise them as not belonging to the landscape and therefore feel annoyed, also by the noise. Experimental studies have shown that the same noise level of traffic generates a higher degree of noise annoyance when pictures of an urban setting rated as not pleasant are shown as compared with pictures of a more pleasant area.20
Annoyance is an adverse heath effect.21
Community noise has in some studies also been linked to other non‐auditory health effects, for example in a recently published study on aircraft noise and hypertension.22
However, these studies have mainly explored sound levels >50 dB(A) and the results are therefore not relevant for effects of wind turbine noise.23
In our study no adverse health effects other than annoyance could be directly connected to wind turbine noise. Reported sleep difficulties, as well as feelings of uneasiness, associated with noise annoyance could be an effect of the exposure, but it could just as well be that respondents with sleeping difficulties more easily appraise the noise as annoying. Wind turbine noise as a hindrance to psycho‐physiological restoration could, however, not be excluded. Being employed was, contrary to the hypothesis, associated with higher prevalence of perceiving wind turbine noise, possibly because individuals who leave the house for work are more observant of stressors that could interfere with their psycho‐physiological restoration needs when at home. Furthermore, respondents who were annoyed by the noise did not think of their living environment as a place for gaining strength. The need for restorative environments in order to maintain health and well‐being, especially for vulnerable groups, has been frequently pointed out, by such authors as Kaplan.24
The fact that a non‐urbanised setting has been linked to restorative properties such as “not being distracted”25
suggests that audio and visual distractions caused by wind turbines could change a rural environment from restorative to non‐restorative.
Of the coping strategies identified, discussing and seeking information appeared to be most successful as this was correlated with less strain. This finding should be acknowledged in the planning of wind turbines, by giving people living in intended wind farm areas relevant information and possibilities to communicate with the developers and authorities.
Our study had some limitations, apart from the difficulties in assessing the exposure mentioned above. Participation was incomplete (response rate 57.6%), but response bias would only explain the influence of urbanisation and terrain if people in one type of area perceiving the noise would be more willing to answer the questionnaires than people in another. This seems unlikely, and similar associations were found when examining those who responded to the questionnaire at the first invitation and those who required one or two reminders (data not presented). It can also not be excluded that differences between the areas, other than terrain and degree of urbanisation, could have influenced the results, for instance local opinion groups and media discussions. Using seven different areas located in different parts of southern Sweden reduced this risk.
The findings of this study are probably relevant for other sources of community noise, such as road traffic and airports. There has been a tradition of focusing on synthesised dose‐response relations for a specified noise source irrespective of environment, even though the results of the studies often differ.27
Difficulties in accurately predicting noise annoyance of particular communities from modelled dose‐response curves has also been reported.28
A recent study of annoyance with noise in an alpine valley, in which data were separately analysed for neighbouring communities, found differences in dose‐response relation between areas; however, the authors do not explain the reasons for the observed differences.29
Future research should not only take into account individual factors already known to moderate the dose‐response relation, such as noise sensitivity and attitude to the source, but should explore the influence of dissimilar environments, in our study associated with perception of and annoyance with wind turbine noise.
- The risk for being annoyed by wind turbine noise increases with increasing A‐weighted sound pressure levels. Dose‐response relation at noise levels as low as these have not earlier been derived.
- Living in a rural environment, in comparison with a suburban area, increases the risk of perceiving and being annoyed by sound from nearby wind turbines.
- Noise annoyance with wind turbine noise could lead to hindrance of human restoration.
- Seeking information and discussing wind turbines as a coping strategy could decrease adverse health effects.
- To avoid annoyance, the characteristics of a geographical area should be taken into account when establishing new wind farms.
- Dose‐response relations between exposure to community noise and noise annoyance should be assessed not just on a general level, but for different living environments.