A new German study suggests the very low frequency sounds generated by the windmill's rotor blades and windflow may be detected by the human brain, going against the theory the sounds are below the threshold of human hearing.

In fact, some people living near these farms have reported sleep disturbances and a decline in overall performance apparently from the \"infrasound' generated by the turbines.  Infrasound, by the way, refers to very low sounds, around 16 hertz, generally thought to be below the limit of hearing.

Similar U.S. studies have come to similar conclusions, citing panic, sleep disturbances, stress, and elevated blood pressure could occur because of wind turbines.  But scientists admit there still needs to be more conclusive data gathered.

The wind power industry dismisses such complaints, saying the sounds generated are too low and faint to be detected by humans.