power line buzzing sound and weather

Factual Questions
1

Last week, I was near Quebec, doing some cross country skiing. It was snowing heavily. I was running a trail that passed under some heavy-duty power lines, and the air around them was FILLED with a rushing/buzzing sound that was so loud that initially I thought that there was a river rushing by somewhere, perhaps buried under snow and I so that I could not see it, but only heard it. However, there was nothing like that nearby, and I assured myself that the sound was coming from the power lines.

The next day, I ran the same trail. The snow had stopped, and the day was sunny. This time, when passing under the power lines, I barely heard anything - I had to stop and listen carefully to catch even a faint buzzing noise.

Why did this happen?

Is there something about the lines themselves? Was it snow in the air reflecting and diffusing sound that was otherwise somehow escaping unheard (like a beam of light in fog or dust)? Humidity?

2

The breakdown voltage for air decreases with increasing humidity. With increasing humidity, the high voltage in the line begins to ionize the air surrounding the line. This is what you are hearing. It is referred to as corona discharge. The buzzing noise is due to the 60 Hz cycling of the electric field. (Actually, there would have been three lines for each of the three phases; each phase is 120 degrees apart.)

3

robby is correct - you notice it especially at power plants by their switchyard, where the lines are much closer to the ground and during times of high humidity (such as early morning fog) the sound can be oppressive.