What makes a long buzzing noise that people say are power lines?

Question

What makes a long buzzing noise that people say are power lines?

Answer 1

It is the Transformers (robots in disguise)

Answer 2

its the transformers

Answer 3

Cicadas aka 17 year locusts.  If you hear the sound about now until the end of summer, that's what it is.  

http://www.cicado.com/cicada-top.JPG