Wind Farm Noise and Infrasound
Giant industrial wind turbines deliver a merciless, thumping, grinding cacophony of daily torment to families forced to live next to them!
The internet is full of video clips amply demonstrating the noise from wind turbines just as it is of anecdotal evidence from those forced to endure it.
Here’s an example from Australia
Perhaps the best information comes from MAS Environmental Limited – an Environmental Health Consultancy and Training business:
Whilst the issues surrounding wind farm noise are greatly discussed and debated, it has been experienced by relatively few in the profession or by those responsible for influencing the decision of whether nearby residents will experience this noise and if so to what extent.
The listening room experience aims to replicate listening to wind farm noise, particularly AM (Amplitude Modulation), in a home situation. Clips of wind farm noise are taken from MAS Environmental’s own measurements in the field and within dwellings where complaints of wind farm noise have been made.
MAS feel that there is a specific need to hear and experience wind farm noise and amplitude modulation not necessarily because of the decibel level of the noise, but largely due to the character of the noise – the changing frequency content and its context within what is usually a very quiet rural environment.
It is not uncommon to hear anecdotal evidence about wind farm noise and character; however, the majority of anecdotal evidence relates to visits to wind farms during day time and typically within close proximity of the turbines. These are not the same conditions or circumstances in which complaints from wind farm noise are made; find out more.
The data used in this graph is taken from a permanent monitoring station located at a resident’s property in the village of Graveley approximately 700m from the nearest of 8 turbines. The station is constantly monitoring noise from the nearby Cotton Farm wind farm. The monitor uploads the noise levels to the internet along with 10m high wind speed and wind direction data taken from a mast located next to the microphone. The uploaded data is freely available for local residents to monitor and log current readings of the wind farm. The residents are given a rating system for highlighting and archiving periods where wind farm noise occurs.
From this monitor we have combined the following short extracts of noise data and audio where the turbines were briefly turned off during a night of EAM that otherwise continued from 9pm on the 18th January until dawn on the 19th January. The church bells marking the beginning of the hour help to give some context to the change of acoustic environment experienced by the residents.
In detail: vibration, infra-sound and low frequency hum/noise
Low frequency noise is often a major problem in nuisance cases and sound at lower frequencies is harder to control. Screening becomes less effective at reducing the noise at lower frequencies, this is because it is less directional and diffuses more easily, travelling around a barrier’s edges. Insulation is also less effective at lower frequencies and thicker and denser materials are required to reduce the level.
When the frequency of the sound is so low that it becomes in-audible to the human ear (usually below 20Hz) we describe it as infra-sound.
Despite not being able to hear the noise, it does not mean that it has no effect on health. It is possible for other parts of the body to be affected by infrasound as the certain low frequencies cause resonance in body parts, for example low frequency sound can affect vision as the human eye resonates at 18Hz.
In 2009 an article was published in the Institute of Acoustics magazine ‘Acoustics Bulletin’. The article proposed changes to the way wind farm noise was assessed primarily relating to the issue of wind shear. It was not based on research or empirical measurements and was developed following some widely stated assumptions about the effects of wind shear. This paper challenges the assumptions made by the article on the influence of wind shear on wind turbine noise and shows that use of this places the protection of nearby residents’ amenity at risk, allowing more noise from wind farms than would be applied using the original principles of ETSU-R-97.
A brief summary of the results of the study is given below:
The table below clearly shows that across all wind speeds for both wind shear exponents assessed that there is no gain in adopting the article method. In 72-75% of cases analysed, the article method actually resulted in a loss of protection to communities. Looking only at the critical wind speeds of 5-7m/s nearly all cases (91-95%) resulted in a loss of protection to communities by using the article method.
The implication of the above results is that by using the article method to assess wind turbine noise, adverse noise impact will rarely be predicted.
This is beneficial for developers as it increases the likelihood that the turbine development will be approved for planning permission. Use of the article method provides a worse situation for local communities as it is more likely to result in adverse noise impact once the turbine development is built despite there being no indication of it at the planning stage and little means for reducing or resolving noise impact post development.
“Evidence to date has clearly shown that the measures proposed will simply not protect families from the negative health impacts of industrial-scale wind turbines. They will condemn families to unnecessary lifelong misery, resulting in a massive waste of people’s time, energy, community money and a clogging of the courts. Communities will not stop fighting this injustice; these guidelines are unacceptable”
Paula Byrne, the Ballyroan-based public relations officer with Wind Aware Ireland