# Cumulative Impact of Wind Farm Noise
## 1 Introduction  
The impact of wind farm noise is especially important when it comes to assessing its negative effects on human health. These effects can be classified into several groups [1]: subjective effects (discomfort, distraction, and discontent); obstruction of everyday activities (conversation, sleep, and studying); and physiological effects (anxiety, tinnitus, or hearing loss at worst) [2; 3]. The most striking issues in their significance so far have been the acoustic impact and sleep disturbance that affect the local population in the areas around wind farms [4; 5]. Sleep disturbance caused by wind farm noise can be singled out as having a particularly significant negative impact due to its health, psychological, and psychosomatic effects, which have been the focus of many research papers [5; 6; 7; 8; 9; 10; 11; 12]. The most striking implications felt and reported by the population settled around wind farms are anxiety, sleepiness, fatigue, irritability, and reduced sleep quality [7; 10], especially if the noise level exceeds 45 dB. Such symptoms are caused by the forced change of sleep patterns, which affects the quality of life, especially for the sensitive and aging population [13]. A number of authors have mentioned infrasound as a noise-related issue resulting from the wind farm operation [14; 15; 16; 17; 18; 19; 20], while some others are more concerned with low-frequency sound [21]. In their comprehensive study of literature on the possible effects of wind farms on the health of the population, [PERSON] et al. [22] conclude that when it comes to infrasound and low-frequency noise produced by turbines in wind power plants, major impacts on people include physical symptoms, general health issues, and affective impact (temper). By analyzing extensive literature, the authors point to the deficiency of properly conducted and comprehensive studies, both clinical and epidemiological, on the potential effects of all kinds of low-frequency noise on the well-being of the population inhabiting wind farm areas. In such a context, certain authors [23; 24] point out the significance of predetermined referential methodology for measuring the impact as well as the need forsetting clear codes for estimating the tolerable level of turbine noise effects, especially if we have in mind many different laws and regulations for determining the limitations of acoustic noise produced by wind turbines in different countries existing today. In addition to its effect on people, wind farm noise also negatively affects biodiversity, or fauna, to be precise, which has been examined by [PERSON] et al. [25]. With all the above said, it would be most convenient to include measures of preventive protection against the possibly negative environmental impact of wind farms as early as the planning stage. The projection of noise effects is even more important if several wind power plants are to be developed in the same area due to their cumulative acoustic impact on the said space, which is, as a rule, stronger than the combined impact of individual wind farms. The most convenient point for addressing the issue of noise impact assessment would be the Strategic Environment Assessment (SEA), as it is one of the earliest documents in the process of project development. Preventive planning at that stage would eliminate issues arising in later stages of project development [26; 27]. That was the case of Cibuk and Vetrozelena, two adjoining wind farms from Serbia presented in this paper. Different methods of projecting wind farm noise levels in the environment have been used across the world. By studying the development of a wind farm noise propagation prediction model, [PERSON], [PERSON], and [PERSON] [28] conclude that the noise propagation prediction model defined by the international standard ISO 9613 offers \"impressive\" precision for the predicted and actually measured noise levels. However, it can be further improved by introducing corrections depending on topographic conditions. After that, [PERSON] et al.