Hearing and Sound Waves

Photograph taken by Josh Gow at the Macarthur Wind Farm

Last week we learnt how the human eye can only detect a narrow band within the electromagnetic spectrum – what we know as visible light. Higher frequency waves are known as ultraviolet waves, X-rays and gamma rays, while lower frequency wavelengths are known as infrared waves, micro-waves and radio waves.

In a similar way, our ears can only detect part of the sound spectrum. Sound is composed of frequency expressed as hertz (Hz) and pressure expressed as  decibels (dB). This site has a simple description of what sound waves look like. Why is understanding about how sound works important? A local example is the controversy surrounding the potential health impacts of the Macarthur Wind Farm.

Since the introduction of the Renewable Energy (Electricity) Act in 2000 and the Renewable Energy Target Scheme in 2009, wind farms have become more prominent in Victoria. However, this has not been without controversy as some people claim that wind turbines can adversely impact the health of individuals living in close proximity. Concerns focus on infrasound noise, electromagnetic interference, shadow flicker and blade glint produced by wind turbines. “Infrasound noise” or “low frequency noise” refers to sound waves inaudible to the human ear (although this varies between individuals). ‘Low frequency noise’ is the term used to describe sound energy in the region below about 200Hz. The rumble of thunder and the throb of a diesel engine are both examples of sounds with most of their energy in this low frequency range.

‘Infrasound’ is also often used to describe sound energy in the region below 20Hz. Almost all noise in the environment has components in this region although they are of such a low level that they are not significant. Noise which has most of its energy in the ‘infrasound’ range is only significant if it is at a very high level, far above normal environmental levels.

Wind Turbine Syndrome(“WTS”) is an alleged condition proposed by pediatrician Dr Nina Pierpoint. She cites a range of physical sensations and effects (including sleep disturbance, headache, tinnitus, ear pressure, vertigo, nausea, visual blurring, tachycardia, irritability, loss of concentration, lack of memory, panic attacks, internal pulsation, and quivering) reported by people living close to wind turbines. Dr Pierpont’s assertions are yet to be published in a peer-reviewed journal, and have been heavily criticised by acoustic specialists. This article by the Drum on ABC claims that “this phenomenon has disturbing hallmarks of mass hysteria or psychogenic illness being whipped up by interests groups connected with climate change denial interests, some of whom have personal financial interests in fossil fuels.”

From the Australian Government National Health and Medical Research Council report – “Wind Turbines and Health” (July, 2012)

  • ‘There is no reliable evidence that infrasounds below the hearing threshold produce physiological or psychological effects’ (Berglund & Lindvall 1995).
  • Infrasound associated with modern wind turbines is not a source which will result in noise levels which may be injurious to the health of a wind farm neighbour (DTI, 2006).
  • Findings clearly show that there is no peer-reviewed scientific evidence indicating that wind turbines have an adverse impact on human health (CanWEA, 2009).
  • Sound from wind turbines does not pose a risk of hearing loss or any other adverse health effects in humans. Subaudible, low frequency sounds and infrasound from wind turbines do not present a risk to human health (Colby, et al 2009).
  • The Chatham-Kent Public Health Unit (Ontario, Canada) reviewed the current literature regarding the known health impacts of wind turbines in order to make an evidence-based decision. Their report concluded that current evidence failed to demonstrate a health concern associated with wind turbines. ‘In summary, as long as the Ministry of Environment Guidelines for location criteria of wind farms are followed … there will be negligible adverse health impacts on Chatham-Kent citizens. Although opposition to wind farms on aesthetic grounds is a legitimate point of view, opposition to wind farms on the basis of potential adverse health consequences is not justified by the evidence’ (Chatham-Kent Public Health Unit, 2008).
  • Wind energy is associated with fewer health effects than other forms of traditional energy generation and in fact will have positive health benefits (WHO, 2004).
  • ‘There are, at present, very few published and scientifically-validated cases of an SACs of wind farm noise emission being problematic … the extent of reliable published material does not, at this stage, warrant inclusion of SACs … into the noise impact assessment planning stage (EPHC, 2009).
  • While a great deal of discussion about infrasound in connection with wind turbine generators exists in the media there is no verifiable evidence for infrasound and production by modern turbines (HGC Engineering, 2007).
  • There are no direct pathological effects from wind farms and that any potential impact on humans can be minimised by following existing planning guidelines. (NHMRC, 2010)

National Health and Medical Research Council Public Statement

“Infrasound from Wind Turbines: Fact, Fiction or Deception?” Geoff Leventhall

What do you think the scientific evidence shows? What are the ‘placebo’ and ‘nocebo’ effects?