Just some related info people might be interested to know. I'm responsible for the maintenance of the High Voltage network within the company I work for. The sound that you hear when near overhead lines is the electricity tracking to earth usually across the insulators at each pole. This is of no concern to the general public or safety and is usually more apparent when raining due to the reduced resistances. Just a little annoying I guess. Transmission voltages around Australia vary depending on areas and the distance electricity needs to be transported. Most common voltages are 500kv 330kv, 132kv, 33kv and 11kv. Your higher voltages like 33kv and above are usually installed on the higher towers allowing greater distance from the public, trying to prevent contact with them. Your lower voltages below 33Kv are mounted on your general power poles which you'll see in alot of urban streets. High Voltage feeders can also be installed in the ground. I find it hard to believe that High Voltage lines cause any sort of cancer due to emf but I haven't spent alot of time studying this. The low frequency radiation from our electricity isn't enough to cause cells within the body to deform or become cancerous. High frequency devices like microwaves and cell phones may be a different story. Only time will tell with those I guess. I think the main concern you would have with purchasing a property with transmission lines within view is, like a few have already said, your resale value.