Why Pacific Hydro commissioned the Cape Bridgewater wind farm acoustic study 

Last week, Pacific Hydro released the report The results of an acoustic testing program – Cape Bridgewater Wind Farm. The report appears to have created a bit of controversy on Australian airwaves and social media channels. The report, which is more than 200 pages long plus appendices, appears to have caused some confusion – partly as a result of misreporting by some media – including why Pacific Hydro commissioned the report and what it actually found.

Pacific Hydro decided to conduct this study to try to better understand the ongoing concerns being raised by a number of residents who live near our Cape Bridgewater Wind Farm in southwest Victoria. As part of our commitment to working with these residents, we allowed them to select the acoustician who would undertake the study, and they subsequently chose Steven Cooper from The Acoustic Group.

The brief to Steven Cooper was to see whether any links could be established between certain wind conditions or sound levels at Cape Bridgewater and the concerns of the six individuals involved in the study. Beyond this, Steven Cooper determined the methodology and also had a fair amount of latitude in terms of scope of the study.

Some have questioned why we would do such a thing. Our response to this is that we have never felt that we have anything to hide. We also had a genuine desire to work with the residents.

Some might call this foolish; we call it the right thing to do.

Below are a few points we feel need some clarification in the discussion about this study:

1) The study found NO correlation for noise or vibration with respect to the operation of the wind farm and residents’ observations.

2) What the study did find, from the limited data set, is a ‘trend’ between the existence of infrasound frequencies and the higher severity levels of sensation as recorded by the residents. This band of infrasound frequencies is below the accepted audible threshold level – basically, such frequencies are unable to be heard by the human ear.

3) Infrasound exists in both the natural and built environment. The question is whether humans do respond to infrasound and at what levels. This requires medical study.

4) This report is in no way a medical study; it is a technical acoustic study. The new concept of ‘sensation’ as introduced in the report was agreed between Steven Cooper and the six individuals who participated in the study.

5) The study was never intended to be scientific study and has not been peer reviewed.

6) Steven Cooper created his own methodology and the ‘wind turbine signature’ is a term used by The Acoustic Group to describe the blade pass frequency and the first six harmonics of a wind turbine. This is not a standard (or accepted) acoustic curve that is used within the industry.

7) We decided to make the study publicly available, i) Because the residents had requested this and it was something we committed to at the outset of the study and ii) simply for transparency purposes.

Some have asked why we would commission such a study if we weren’t prepared to do anything with it.

The answer to this is that we did not know what the study would reveal at the outset. We were always prepared to address any issues that were found to be quite evident or that led to a strong conclusion. In this case, we do not believe the study has found anything strong enough to warrant further action. We will not be conducting any more studies at this stage ourselves, but we would welcome further study by others.

It is important to note this study is simply part of a broader program that we are continuing with our local communities. We will continue to work with the Cape Bridgewater community and other local communities in which we operate.

We continue to welcome the discussion that the report has generated, as we believe no company or industry is above reproach and we should always strive for standards that are publicly acceptable. Pursuing a better understanding of the impacts of all human activities on both our environment and our communities is one we should never relinquish. We hope others can look beyond some of the inaccurate reporting so that a mature, informed discussion can occur.

Andrew Richards is executive manager of external affairs at Pacific Hydro.