The construction of wind turbines and their potential impact have generated many conflicting emotions in society. Unfortunately, substantive discussion often tends to be replaced by political confrontation where the aim is not to seek the truth but to shape it to suit economic or ideological interests. This is compounded by a limited willingness to acknowledge uncertainty, accept the limits of science and engage in reasoned dialogue even with those who think differently.

Such an attitude — and the use of scientific consensus as a hammer — reflects not so much a commitment to science as a lack of societal maturity. The aim of this article is to point to the absence of open and constructive debate and to society's immaturity in addressing controversial issues.

Scientific consensus and fact checking — a hammer for every situation

Increasingly, expressions such as "scientific consensus" or "I trust science" are used in public debate as rhetorical weapons. These concepts are often employed in ways that lead to the dogmatization of science. Yet science is not based on belief or final truths, but on constant doubt, criticism and the accumulation of new evidence. Classical works in the philosophy of science likewise emphasize that consensus may arise as a practical agreement, but it does not represent an absolute or eternal truth.

In science, it is natural for positions of varying reliability to exist, which is why shutting down scientific debate merely by referring to consensus resembles religion more than science. The "scientific consensus" hammer is justified in fields that have been studied thoroughly over a long period of time, but not where knowledge is incomplete, results depend on methodology and phenomena are strongly context-dependent.

In this light, a statement made last year by Social Affairs Minister Karmen Joller — that "scientific consensus" does not consider infrasound produced by wind turbines to be harmful to humans — also requires clarification.

At best, this claim is incomplete. It is true that studies to date have not demonstrated a universal and direct harmful effect of infrasound on all people up to a certain sound pressure level. However, this does not mean that the effect is entirely absent or the same for everyone. In medicine, it is well known that people's responses to both environmental influences and medications vary significantly and depend on a number of factors, including genetic characteristics, health conditions, age and the level of sensory sensitivity. Similarly, people's auditory perceptions differ at various frequencies and sound pressure levels.

Peculiarities of auditory perception

The perception of noise and sound, including low-frequency sound and infrasound, is also clearly individual. People differ in their hearing perception, depth of sleep and sensory sensitivity. Some people wake up at the slightest crack, while others are not disturbed even by strong background noise. Similarly, noise at different frequencies may be disturbing to people in different ways.

A claim presented in a Postimees fact check — that the disturbing nature of noise is determined primarily by sound pressure — is simplified and does not adequately address the role of frequency changes, especially considering the specific perception mechanisms of low-frequency noise and infrasound.

Both frequency and changes in frequency influence perception and biological responses (for example, excitement and emotional reactions). Put simply, infrasound does not compress the air more; rather, it moves it over a much greater range and more slowly and it is this movement that may affect the human body, the auditory and balance systems and the surrounding environment, even when we do not hear the sound.

Auditory perception is not limited to "hearing" in the classical sense. Low-frequency stimuli activate both the auditory system and bodily sensation (the somatosensory system) as well as the balance and motion perception (vestibular) system simultaneously.

Medical studies have confirmed that the function of the Eustachian tube — the regulator of pressure in the middle ear — varies both between individuals and within the same individual over time. Likewise, it has been established that certain pathologies and physiological conditions (including congenital anatomical and nervous system differences) may make a person more sensitive to low-frequency sound and infrasound.

For this reason, it cannot be ruled out that low-frequency sounds or infrasound may in certain circumstances be perceptible and disturbing for some people. Consequently, it is difficult to automatically reduce complaints from people living near wind farms to purely psychosomatic causes — that is, the appearance of physical symptoms primarily due to mental or emotional factors. Although mental and social factors do play a role, they alone cannot explain phenomena whose physiological mechanisms are not yet clear or sufficiently studied.

Engineering-technical view

From an engineering perspective, it is a fact that wind farms produce both audible noise and infrasound. Infrasound generally remains below the threshold of hearing, but under certain conditions it may cause or trigger audible disturbances. For example, pressure fluctuations can cause structural elements in buildings — doors, ventilation dampers and lightweight partition walls — to generate audible noise.

Such noise (for example, the banging of ventilation dampers) is undeniably easier to perceive at night, when overall background noise is low. Noise and phenomena audible to the human ear can disturb some people's sleep even when the applicable regulatory limits are not directly exceeded either inside or outside the building. The harmful effects of noise on sleep quality, mental health and the cardiovascular system are well documented in the scientific literature and include both short- and long-term impacts.

The above is not refuted by a study on the health effects of wind turbines compiled by researchers at the University of Tartu based on peer-reviewed scientific literature. The study focuses on health effects in the narrow, medical sense and leaves in the background intermediate impacts — chronic disturbance, stress and declining sleep quality — which do not appear in medical diagnoses but directly affect quality of life.

Disturbance is treated more as a side effect, although over the long term it may precede sleep disorders and stress-related problems. Several conclusions are based on short-term laboratory experiments and average values from noise models, which do not adequately describe long-term living near wind farms or situations where sound changes significantly over time and frequency under stronger winds and certain wind directions.

Vulnerable groups — such as noise-sensitive individuals or residents with certain health conditions — are addressed only to a limited extent. For this reason, the study cannot be interpreted as final confirmation or as "scientific consensus" that the impact of wind turbines on human health is negligible in all circumstances. It is therefore reasonable to ask whether, given current knowledge, we can confidently claim that the addition of infrasound sources to the surrounding environment will have a negligible effect on the future budget of the Health Insurance Fund.

Specifics of measurement and unnecessary comparisons

Large wind farms may also exhibit physical phenomena such as the short-term sharp amplification of sound at certain frequencies (constructive interference, resonance) and accompanying sounds (harmonics).

As noted, sudden changes in pressure may directly or indirectly disturb people with certain pathologies. As a result, the noise spectrum may change and manifest within the audible range for humans. Such amplification depends on the placement of turbines, wind direction and the surrounding environment.

In the case of the Sopi-Tootsi wind farm noise study, it is important to highlight methodological limitations. It is unclear why the measurements were not carried out in accordance with the turbine emissions standard. One-third-octave measurements provide a general overview but smooth out rapid sound changes. One-thirty-sixth-octave analysis shows sound much more precisely and helps better identify specific tones and sudden amplifications in sound pressure and their interaction, such as resonances, constructive interference and harmonics.

By comparison, this is like measuring a car's speed as a 12-second average rather than a one-second average — when overtaking, you might not even notice that you exceeded the speed limit. Another comparison: how would you feel if heart function were assessed only by average pulse rate, where clinically significant arrhythmias and short-term deviations in heart rhythm would go unnoticed?

In addition, the measurements were carried out mainly at wind speeds at which complaints occur less frequently, while several sources indicate that disturbances tend to appear during stronger winds and under certain wind directions.

It is also not correct to directly compare infrasound from wind turbines with that produced by vehicles, as is sometimes done. In the case of turbines, the dominant frequency range usually remains between 0.5 and 8 hertz, whereas inside a vehicle cabin it is roughly 6 to 18 hertz and in the external environment about 1 to 6 hertz. It is also important to add that, in addition to frequency, the shape of the noise spectrum, duration, amplitude and variability of amplitude all influence perception.

Where to go from here?

In conclusion, it is not fair to make things sound better than they are; references to "scientific consensus" should also cease in situations where our knowledge is in fact incomplete. In Estonia's public institutions, the quality of studies needs to be improved and greater political independence ensured in decision-making on both energy and medical issues, as these directly affect public health and economic well-being.

While involving researchers can certainly help improve the quality and reliability of studies, peer review of commissioned research should become standard practice in the case of studies with significant impact. Studies and measurements (including noise studies) should be conducted based on the latest knowledge, using accredited measurement methodologies and measurement approaches that allow acoustic and other phenomena to be identified more precisely.

In several foreign countries, or in their states or regions, turbine setback distances are clearly linked to turbine height, which better takes into account the acoustic, visual and psychological well-being of local residents and does not reduce property values. The issue is not limited solely to possible health effects, but concerns the overall quality of the living environment.

The involvement of communities in planning such developments is a natural part of the democratic decision-making process and does not mean ignoring science, but rather the need to make decisions based on sufficient, honest and transparent information.

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