hum from nearby high-tension wires?

>>"These aren't the monster tower kind of transmission lines for long distances, they are local distribution type within city limits that have lower emissions."<<
[Steverw]
>>>>>>>>>

Just curious how high off the ground would you say the power lines are?

How long are the insulators that the wires are supported by?
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>>"There is also a large transformer station of some kind about 200 feet away."<<
[Steverw]
>>>>>>>>>>>

That sounds like a Substation. Just an example of a Substation in a residential area, 3 phase 69KV feeding the Substation 7.2KV/13.2KV 3 phase 4 wire out.

Substation near a large university could be 169KV feeding the Substation.

Best guess, how high are the power lines, and the size of the insulators?

I think the hum should be the last thing your concerned about.

Jea48: maybe 80 feet high. Insulator about the height of a large owl or hawk (maybe a foot?) (I often see them sitting on the line).

Dreadhead: well, consider that I live in an earthquake zone and commute some 75 mi per day; these are probably my biggest risks. And just being 49 years old has its risks - bell-curve-wise, many of me are already dead. I don't smoke, but I like wine; my cholesterol is moderate, but on the high side (along with my weight). And I drink tap water. EM from the power lines ranks below these other things on my list of threats to life.

At least I want to enjoy music while the radiation crisps my genetic material.

(Please note that I'm attempting to make light of the situation, I hope no one is offended by these off-hand remarks. All of us have had loved ones who have been affected by various unpleasant health issues, and I mean no disrepect, I'm just being flippant to put some emotional distance between me and the consequences of taking risks.)

Update: it may be due to poor grounding of the house. I found the ground spike, connections to it are corroded. Plus I found a degenerate cable connection that was not in use. Oddly, disconnecting this hidden cable connection actually made the hum louder. I need to get an expert in here to asses the house grounding.