Dr. Chris Hanning:

Before dealing with the questions posed, I will expand a little on my expertise to speak on this issue. The committee has heard that I am a retired consultant in sleep disorders medicine. I am also a published author in the field of wind turbine research and health. I have given evidence at planning inquiries in Ireland, England and Canada. I have also given evidence before the Australian Senate.

The purpose of set-backs and guidelines is to protect the human population. Therefore, we should examine the effect on the human population in determining what is an appropriate distance between turbines and human beings.

To answer the second questioner first, for some time I have held the view that 1.5 km is an appropriate set-back distance. I understand a Bill has been tabled to allow for a distance ten times the height of turbines, which is equally satisfactory. That estimate is based on existing research on real human beings and real wind farms. The guideline noise levels tend to have been derived from studies of traffic noise. Wind turbine noise is several times more annoying than traffic noise at the same sound pressure level. They do not seem to have the same effect on humans. Wind turbine noise is more annoying and has a greater effect. Therefore, it is not appropriate to use data derived from studies of traffic to devise noise guidelines in respect of wind farms. The evidence we have is that if people are exposed to an external noise level of 43 dB, they are at high risk of sleep disturbance.

Deputy Willie Penrose also asked about low-frequency noise and infrasound. This is a slightly unsettled area. For many years we have known that research shows low-frequency noise and infrasound adversely affect human sleep and human health. The mechanism is unknown, but there are preliminary ideas from Professor Salt in America that the ear responds to inaudible sound. It does not matter what has caused the harm, whether it is low-frequency noise, audible noise or pulsatile noise. We do not wait to take action on public health issues until every aspect of the causation has been settled. We have sufficient evidence of harm from the studies carried out of existing wind farms to take action now.