1.5 kilometers Dr. Chris Hanning (UK) - Cape Cod Commission

Wind Turbine Sound and Health EffectsAn Expert Panel Review, December, 2009I. Dr. McCunney Presentation and Testimony• “The origin of this amplitude modulation is not fully understood. It was previouslyassumed that the modulation was caused when the blade went past the tower (giventhe tower disturbed the airflow), but it is now thought to be related to the difference inwind speed between the top and bottom of the rotation of a blade and directivity of theaerodynamic noise (Oerlemans and Schepers, 2009).In other words, the result of aerodynamic modulation is a perceivable fluctuation in thesound level of approximately once per second. The frequency content of thisfluctuating sound is typically between 500 Hz and 1,000 Hz, but can occur at higher andlower frequencies.” (3-5)• “Sounds from wind turbines were found to be more annoying than several otherenvironmental sources at comparable levels…The dominant quality of the sound was aswishing, the quality previously found to be the most annoying type.” (3-15)• “Response to wind turbine noise was significantly related to exposure expressed as A-weighted sound pressure levels dB. Among those who could hear wind turbine sound,annoyance with wind turbine noise was highly correlated to the sound characteristics;swishing, whistling, resounding and pulsating | throbbing (Pedersen, 2008).” (3-16)• “Wind speed at the hub height of a wind turbine at night may be up to twice as high asduring the day and may lead to annoyance from the amplitude modulated sound of thewind turbine (van den Berg, 2003)” (3-16)• “The main health effect of noise stress is disturbed sleep, which may lead to otherconsequences.” (4-3)