I walk to work every morning and pass under some HV power lines. On high-humidity days, there's an audible crackle/sizzle emanating from the lines. I never hear this on the way home.
I would expect this to come from condensation on the insulators, but curiously it is audible only in the center of each span. My first guess is that it's produced all along the wire but audible in the middle because that part is so much closer to the ground.
My question is: If there's enough leakage into the air that I can hear it, doesn't that represent a huge loss over miles and miles of wire?