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Peer review of Collector Wind Farm noise assessment  

Author:  | Australia, Noise, Regulations

The Marshall Day Acoustics report is similar to that provided by that organisation for other wind farms and would appear to fall into a generic type of report, subject to the additional requirements of the draft NSW guidelines to consider night time operations separately to day time operations under “worst case scenarios” and dB(C).

The report appears to be more comprehensive than other generic “acoustic reports” accompanying wind farm applications.

However there are a number of issues arising from this generic approach.

One issue of concern in relation to the generic type of noise assessment prepared by Marshall Day Acoustics for the subject wind farm is that there is a conflict between the title of the report and the contents of the report.

The report is titled “Collector Wind Farm Noise Impact Assessment” yet the report has not actually identified the noise impact that will be generated by the proposed wind farm. This would appear to be a fundamental failure in the obligations of the author(s) of the acoustic assessment i.e. a failure of the obligation to provide a meaningful document in relation to actual noise impacts that the community can understand.

The acoustic assessment has not explained to the community the impact that the proposed wind farm will have upon the existing acoustic environment of the area nor whether the operation of the wind farm will affect their daily activities or their night time sleeping patterns. Complaints from residents in proximity to Capital and Cullerin wind farms frequently refer to sleep disturbance.

Marshall Day Acoustics is aware of complaints from the community concerning wind farms and the impact that the wind farms are creating on residents.

However, despite there being Marshall Day Acoustics reports/compliance tests for the Waterloo wind farm (in South Australia), the Waubra wind farm (in Victoria) and the Te Rere Hau wind farm (near Palmerston North in New Zealand), where there are numerous complaints and instances of people leaving their properties because of the wind farm operations, there is no identification or consideration of the acoustic impact of the proposed wind farm.

The ambient data reveals the existing acoustic environment of the area is significantly less than the base level of 35 dB(A). This automatically raises the question of “What is an acceptable noise impact from the proposed wind farm?” This is not an exercise that has been carried out in the subject assessment by Marshall Day Acoustics.

The acoustic report considers that the description of the acoustic impact is satisfied by identifying compliance with a noise target set out in the SA EPA Guideline, the draft NSW guideline and EPA criteria applied in suburban areas.

However, any experienced acoustic engineer would be aware that generating a noise which is significantly greater than the existing ambient background level of an area can create an impact which should be assessed. …

Bearing in mind that the Marshall Day Acoustics report does not discuss the actual acoustic impact of the proposed wind farm and has not identified the acoustic amenity that residents currently experience then it would appear the predicted noise levels provided in the acoustic report will result in a loss of acoustic amenity.

The acoustic assessment purports at times to indicate that a conservative approach has been adopted in assessing the predicted noise emission levels but would not appear to identify the variation in noise levels that would occur as the result of weather conditions when compared to a worst-case scenario of propagation.

For example, one can have the turbines operating whilst at residential receivers there is absolutely no wind, which is not a situation identified in the acoustic assessment.

The Marshall Day Acoustics report has not identified the relationship between the wind speed at the nominal hub height versus the wind speed at receiver locations. There is therefore no correlation with the predicted noise levels under the wind scenarios that have been assessed, nor identification of the difference in propagation for different wind directions. Nor is there identification of the frequency of the occurrence of adverse meteorological effects which could be identified in a generic term as temperature inversions, separately to the more detailed and complex analysis attributed to the van den Berg effect.

It is quite likely that such an analysis could show a range of noise levels and identify to the community that for a certain percentage of the time the wind farm would be inaudible/barely audible/clearly audible. Such an analysis would provide a clearer interpretation as to the acoustic impact of the proposed wind farm. …

The assessment report has failed to identify the potential audibility of turbine noise outside or inside residential dwellings, which therefore is a significant failure of the report in providing appropriate advice to the community as to the likely acoustic impact. The community called understand the concept of hearing a noise versus not hearing a noise, yet the Marshall Day Acoustics report has not identified the audible impact of the proposed wind farm external to dwellings.

The Marshall Day Acoustics report has failed to identify the potential audibility of turbine noise inside residential dwellings, or the spectral content of the wind farm sound at residential properties. The attenuation of building elements provides a greater degree of attenuation at high frequencies to that at low frequencies. Therefore the spectral balance of noise detected outside a dwelling is different to that inside a dwelling.

Download original document: “Peer review of Collector Wind Farm noise assessment

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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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