Nature: Wind Turbine Noise Issues

Ed. Note: The health effects of industrial wind on local residents continues to attract mainstream research despite severe political incorrectness. It’s common sense: huge industrial machines moving in the open air have negative effects. For other posts at MasterResource on this subject, see here. This post complements yesterday’s on the nighttime amplification of noise.

“Wind turbines generate low-frequency noise (LFN, 20–200 Hz)…. [which causes] headaches, difficulty concentrating, irritability, fatigue, dizziness, tinnitus, aural pain sleep disturbances, and annoyance. Clinically, exposure to LFN from wind turbines may cause increased risk of epilepsy, cardiovascular effects, and coronary artery disease.”

“In order to reduce LFN transport from outdoors to indoors, we recommend that the windows should be kept closed, especially at nighttime because LFN is most noticeable at night. In addition, … residences in close proximity to wind turbines should be equipped with airtight windows.” (Nature, September 8, 2021)

Make no mistake: the obvious is becoming mainstream despite the protests of the mighty industrial-wind complex. The latest evidence on aerodynamic noise comes from Nature magazine [Scientific Reports volume 11: 17817 (2021)]: “Effects of Low-frequency Noise from Wind Turbines on Heart Rate Variability in Healthy Individuals.”

The Abstract follows:

Wind turbines generate low-frequency noise (LFN, 20–200 Hz), which poses health risks to nearby residents. This study aimed to assess heart rate variability (HRV) responses to LFN exposure and to evaluate the LFN exposure (dB, L_Aeq) inside households located near wind turbines.

Thirty subjects living within a 500 m radius of wind turbines were recruited. The field campaigns for LFN (L_Aeq) and HRV monitoring were carried out in July and December 2018. A generalized additive mixed model was employed to evaluate the relationship between HRV changes and LFN. The results suggested that the standard deviations of all the normal to normal R–R intervals were reduced significantly, by 3.39%, with a 95% CI = (0.15%, 6.52%) per 7.86 dB (L_Aeq) of LFN in the exposure range of 38.2–57.1 dB (L_Aeq).

The indoor LFN exposure (L_Aeq) ranged between 30.7 and 43.4 dB (L_Aeq) at a distance of 124–330 m from wind turbines. Moreover, households built with concrete and equipped with airtight windows showed the highest LFN difference of 13.7 dB between indoors and outdoors. In view of the adverse health impacts of LFN exposure, there should be regulations on the requisite distances of wind turbines from residential communities for health protection.

Introduction

Wind energy is used around the world as a source of clean energy. However, wind turbines generate low-frequency noise (LFN) in the range of 20–200 Hz. As many community complaints have centered around the LFN from wind turbines, it is important to evaluate the health impacts of LFN on residents near wind farms.

LFN exposure has been found to cause a variety of health conditions. Exposure to LFN from wind turbines results in headaches, difficulty concentrating, irritability, fatigue, dizziness, tinnitus, aural pain sleep disturbances, and annoyance. Clinically, exposure to LFN from wind turbines may cause increased risk of epilepsy, cardiovascular effects, and coronary artery disease.

It was also found that exposure to noise (including LFN) may have an impact on heart rate variability (HRV). HRV is the variation over time of the period between adjacent heartbeats, which is an indicator of the activities of the autonomic nervous system, consisting of the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). Autonomic imbalance usually represents a hyperactive SNS and a hypoactive PNS and results in reduced HRV.

An autonomic imbalance may increase the morbidity and mortality of cardiovascular diseases²⁵. A review paper indicated that road traffic noise may overactivate the hypothalamic-pituitary-adrenocortical axis (HPA) and sympathetic-adrenal-medullar axis (SAM), increase the blood pressure and reduce HRV, and finally affect the cardiovascular system²⁶. A recent study analyzing 658 measurements of HRV obtained from 10 healthy males (18–40 years old) indicated reductions in HRV due to environmental LFN exposure²⁷. However, few studies have specifically examined the effect of LFN from wind turbines on HRV in healthy individuals; thus, this was the aim of this study.

In view of the adverse health impacts of noise exposure, many countries and international organizations have established regulations for noise control. These regulations are set for noise in the full spectrum of human hearing (20–20 k Hz). The Ministry of Environment of Finland set limits for wind farm noise of 45 dB (L_Aeq) during the day and 40 dB (L_Aeq) during the night.

In the United Kingdom, the fixed limit for turbine noise is 40 dB (L_Aeq) for the daytime and 43 dB (L_Aeq) for the nighttime. In the United States, noise levels of ≤ 55 dB (L_Aeq) are set for outdoors in residential areas, farms, and other outdoor areas as requisites for public health protection, and levels of 45 dB are set for indoor residential areas, hospitals, and schools.

In addition to the full noise spectrum, the Taiwan Environmental Protection Administration (EPA) also established regulations for LFN to avoid impacts on residents, since wind farms have been set up very close to residential communities. The LFN standards for wind turbines in the daytime (7 a.m.–7 p.m.) and evening (7 p.m.–10 p.m.) are 39 dB (L_Aeq) for environments requiring tranquility such as residential areas, 44 dB (L_Aeq) for mixed residential and commercial/industrial areas, and 47 dB (L_Aeq) for industrial areas; those at nighttime (10 p.m.–7 a.m.) are 36, 36, 41, and 44 dB (L_Aeq), respectively³². This study assessed the LFN in the indoor environments of households near wind turbines to evaluate whether the LFN levels meet the Taiwan EPA standards.

One of the most important factors influencing residential noise exposure from wind turbines is the distance of the wind turbine from the observer³³. For example, at a distance of 120–500 m, the measured turbine noise levels decreased by 3–5 dB (L_Aeq), while at a distance of 1000 m the noise was reduced by 6–7 dB (L_Aeq). Hansen et al. reported variations in indoor LFN levels (15–45 dB (L_Aeq)) for two households (houses made of sandstone/concrete/iron or bricks with windows remaining closed or half open) at different distances from wind turbines.

This study assessed the indoor/outdoor differences in LFN exposure in several households located at varying distances from wind turbines. Our main focus was on the indoor LFN levels in several recruited households; we did not intend to conduct a comprehensive evaluation of the influential factors. These households serve the purpose of demonstrating the potential impacts of influential factors.

Besides distance from turbines, building materials also affect indoor LFN exposure. This work assessed the indoor LFN levels for several recruited households with different building materials and open/closed windows to illustrate their potential impacts. It is known that materials have different sound absorption coefficients.

The overall sound pressure level and spectrum of external noise change when transmitted to the interior of a building. Mid- and high-frequency noises are selectively attenuated by roofs and walls, causing the building structure to function like an LFN pass filter.

Outdoor to indoor noise reduction generally decreases with frequency, which is related to housing construction and room dimensions. Factors contributing to indoor/outdoor noise reduction also include structural resonances, room modes, and coupling between the air volume inside the residence and the stiffness of the walls, roofs, and ceilings. It is known that the appropriate choice of construction materials and designs can contribute to LFN exposure reduction for residents. Hence, these factors are not evaluated comprehensively in this study.

Taiwan is a small and highly populated island. Wind farms have been set up near residential communities, affecting the day-to-day lives of the residents. The hypothesis of this study is that LFN from wind turbines might affect HRV of residents. In order to verify the hypothesis of this study, we defined two objectives: to evaluate the LFN and HRV relationship with an intervention design and to assesses the actual LFN exposure of the community residents.

This investigation is the first in Asia examining the impact of LFN from wind turbines on the HRV of healthy residents. In addition, the variations in LFN exposure inside several residences constructed of different building materials are examined. The findings of this study would serve as a useful reference for Asian countries planning to launch or promote wind power generation.