Why Do Power Lines Buzz?

The buzzing sound that power lines produce is caused by corona discharge. Corona discharge is an electrical discharge that occurs when a fluid (like air) surrounding an electrically-charged conductor becomes ionized. In simple terms, its the noise that air (surrounding the power lines) makes as electricity jumps through it. Mains hum, electric hum, or power line hum are generally used to refer to the sounds produced by transformers or power lines due to the alternating current at the frequency of the mains electricity. Typically, the fundamental frequency of the buzzing sound you hear is 50 or 60 Hz, depending on the local power line frequency.