Natl Assoc of Regulating Utility Commission (NARUC)

Summary note:  

We propose 35 dBa at nighttime and 40 dBA daytime to avoid negative impact to persons living near industrial wind turbines. The county proposes 50 dBA at all hours which is equavalent to trying to sleep with a person having a conversation in your bedroom.  Levels of 40-45 dBa sound level have relatively high annoyance rates of 20-25% so 1 out of 5 or 1 out of 4 people living within 2000 ft.  Rural areas during night time hours can have lower background sound levels of 25 dBa so turbine noise is more noticeable to residents.  For every 10 dBA increase it is a doubling of the noise level.  A level of 40 dBa doesn’t mean the turbine is inaudible or completely insignificant only low enough that not considered objectionable by majority of the neighbors.  Wind turbines have a distinctive, identifiable character more readily perceived/noticeable.