FROM Mr Soames’s letter (August 13) he either did not attend or did not understand the issue specific hearing on noise in the Navitus Bay examination.

There are in fact two equally important issues, construction noise and operational noise, which were addressed on behalf of residents by myself and another independent expert acoustician at the hearing.

On construction noise the applicant simply failed to do the sums correctly; the piling noise would be loud enough to cause serious annoyance well inland of the shoreline around the proposed turbines. Because of the immense scale of the project, and the requirement not to disturb sleep at night, piling would last for years, not just months.

As for operational noise, the Institute of Acoustics, of which I and the applicant’s acoustician are members, has published guidance for the assessment of wind turbine noise propagation paths over long stretches of water, which all parties agreed should apply to Navitus Bay.

Using that guidance even the applicant’s final downsized 630 MW version of the project, when correctly calculated using measured noise emission data typical of real turbines, shows onshore noise levels somewhat in excess of Government limits.

The simple fact is that sound propagates very efficiently downwind over water, as it is both reflected by the sea and refracted by wind shear (wind speed increases with height above sea level), so effectively reaches the shore in several “hops”.

This isn’t a new theory; it was proposed in “On the Refraction of Sound by the Atmosphere” in the Proceedings of the Royal Society of 1874 and 1875 by Professor Osborne Reynolds, and demonstrated by him in the Wash.

There are several reasons why there have been few noise complaints about existing offshore wind farms.

All those currently operating around UK shores are so much smaller than Navitus Bay. Several are closer to the shore, but often spread out in a line, not concentrated in a matrix.

Finally most are off the East Coast, and therefore downwind (in the UK’s prevailing SW wind) of the shoreline. In fact no other offshore wind farm anywhere near the proposed size of Navitus Bay size has ever been built so close to, and upwind of, such densely populated and recreational shorelines.

I hope this helps Mr Soames to better understand the Navitus Bay noise problems.

JOHN YELLAND

MA DPhil (Oxon) MInstP FIET MIOA