What does electrical hum sound like?

An electrical hum typically sounds like a low-frequency, continuous acoustic drone or vibrating buzz, usually pitched around 60 hertz matching the alternating current frequency of the electrical grid. This sound is caused by electromagnetic induction and mechanical vibration as current flows through transformer coils, magnetic ballasts, or loose switch terminals, making metallic components vibrate rhythmically. It differs sharply from the crackling or popping sound of electrical arcing. You can troubleshoot acoustic sounds safely by listening to locate the source. You can verify that your corrective action is successful when tightening loose terminal screws, replacing vibrating ballasts, or installing insulated fasteners eliminates the low-frequency drone entirely and restores a quiet environment.