Powerful sound
Question: Walking through the countryside last weekend I noticed the overhead
power lines were emitting a very loud hum. What causes this noise in
high-voltage cables?
Answer: The hum is the result of the alternating electric field affecting
water on the surface of the power line.
Possible mechanisms include vibration of the water surface caused by the
field, spitting from the tips of water droplets (corona discharge), or the rapid
expansion of the air at the tips, due to heating.
While the details of how the noise is actually produced are not clear, we do
know a good…
