Marshall Day Acoustics has relied solely upon the EPA Guidelines and has ignored the acoustic characteristics that residents will actually receive as a result of the Stony Gap Wind Farm. They have not addressed the actual acoustic impact of the wind farm on the community.
The Marshall Day acoustic assessment provides a set of predicted noise levels in terms of the A-weighted values set out in the Guidelines and concludes that there are no tonal or modulation characteristics requiring modification to the predicted noise levels.
The assessment does not specifically address the influence or effect of winds and temperature inversions which have the potential to result in higher noise levels than have been predicted.
Professor Hansen has raised the issue that the acoustic assessment has under predicted the noise that residents will receive and taking into account the above matters, there is the distinct possibility that at times noise generated by the proposed wind farm will be greater than that set out in the acoustic assessment.
In relation to background levels, the attached measurement results confirm (as expected) that ambient background levels inside rural properties in the subject region are significantly lower than 30 dB(A) and that external noise levels are lower than the nominated Environment Protection (Noise) Policy 2007 night time Indicative Level of 40 dB(A) for rural areas. As such, the noise generated by the wind farm is likely to be significantly greater than background +5dB(A) and therefore to have an impact significantly greater than for an “annoyance.”
The issue of low frequency noise and infrasound has been raised and discussed above. Documentation from the world’s leading supplier of turbines has identified that computer models are inadequate for low-frequency noise propagation. As high frequencies are rapidly attenuated over distance (when compared to low frequencies) audible characteristics of the turbines may be reduced to a low frequency hum and can also include frequencies below the normal range of human hearing.
The Guidelines identify that infrasound is not generated on a well maintained wind fann yet the measurement results obtained for the purposes of this report prove otherwise. The measurement data appended to this review identifies that there are both low frequency and infrasound components generated by the turbines that are currently located in the region.
A proper assessment of community impact (either pursuant to the Development Plan or generally) cannot ignore low frequency noise and “infrasound.” To the extent that it does, when these have been issues of specific complaint with other wind farms, the Marshall Day report falls short of its responsibility to the community.
The Guidelines identify that for host stakeholders, sleep disturbance is an adverse health effect. It is not unreasonable for Council and the community to assume that if sleep disturbance gives rise to an adverse health effect for persons who are obtaining a financial gain from hosting turbines, then sleep disturbance that impacts upon the general community (i.e. non-host stakeholders) must also give rise to an adverse health effect.
This peer-review has identified two eminent acousticians who, in 2002/2004, identified that there are issues with low frequency and infrasound and that the ear still continues to work and receive signals even when people are asleep. The mechanism causing sleep disturbance (for example, whether individuals are able to detect the infrasound components) is an issue outside my expertise.
But it is clear that use of the A-weighted value for assessment or compliance purposes does not address all of the noise impact issues associated with wind farms.
The Council’s Development Plan requires certain objectives to be met for the subject wind farm. These objectives have been outlined above. The current application has not satisfactorily addressed these objectives, and has not actually assessed the noise or the impact of the subject development.
Inadequacies of the EPA Guidelines in meeting their own core objects have been raised. Council may consider raising these difficulties which the Guidelines are causing the Council with the EPA to address the concerns of the community.
As a result of the various matters raised and outlined above, there can be no confidence that the community will not be adversely impacted by the proposed Stony Gap Wind Farm. It is recommended that Council should request further particulars from the Applicant to address the individual matters raised above with particular reference to the Development Plan and with a view to identifying the actual noise impact that will be generated by the proposed wind farm.
Download original document: “The Acoustic Group – Peer Review of Noise Impact Assessment”
A: Curriculum Vitae, Steven Cooper
B: Australian Acoustical Society Code of Ethics
C: Hearing Response and Weighting Curves
D: Turbine Sound Power Levels
E: 1/3 Octave Band Results
F: Turbine Modulation
G: Narrow Band FFT Spectra
H: Ambient Measurements – Hallett 3
I: House 6 Measurements
J: Photo Across Valley
This article is the work of the author(s) indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.
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