EXPOSURE TO INFRASOUND AND LOW FREQUENCY NOISE, ORIGINATED BY WIND TURBINES – A GEOGRAPHICAL ANALYSIS
Background: Despite technological advances to make wind turbines quieter, they still produce sounds resulting from their mechanics and aerodynamics, namely infrasound and low-frequency noise. This noise affects the quality of life and can develop acoustic processes that are not processed by the ear and cause irreversible injuries to the human body.
Aim: This study aimed to analyze the wind turbines noise behavior based on distance to source, air velocity and wind direction. It also aimed to measure the sound pressure level produced by wind turbines and to analyze the difference between Infrasound and Low Frequency Noise and Environmental Noise.
Methods: Three wind farms (district of Leiria, Portugal) were selected, where a total of 416 measurements were performed. The type of study was transversal, cohort observational and sampling was probabilistic in type and convenience in technique. Measurements were performed with the CESVA SC420 sound level meter. The measurements were taken taking into consideration the cardinal and collateral points around three wind farms. The measurement points were defined at distances: 0; 0.5; 1; 2; 3; 4; 5; 10; 15 km. Four types of noise were evaluated, classified as: Infrasound (2-20 Hz/dB), Low Frequency Noise (20-500 Hz/dB), Infrasound and Low Frequency Noise (2-500 Hz/dB) and Environmental Noise (dB(A)).
Results: It was found that the distance to the source is not a relevant factor in the reduction of noise levels and to higher the air velocity, higher sound pressure levels. It was also found that the points “South” and “Southwest” were where there were higher noise levels. Other factors were relevant in the propagation of noise, namely: terrain profile; caves; proximity to the shore; forests. There is a very significant difference when comparing measurements in dB or dB(A), especially in infrasound, which reinforces the need to assessed this noise as an agent that may have other biological impacts than deafness.
Conclusion(s): It is concluded that it is important to adopt territorial management measures taking into account the protection of public health, particularly in the installation of wind farms at safe distances and to include infrasound and low frequency noise in environmental impact studies.
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