This sound often vibrates at 60 Hertz (Hz), matching the frequency of the alternating current (AC) supplied by the utility company. This steady, quiet hum is typically caused by the magnetic fields generated within the main transformer or when the panel is under a heavy. The electrical service panel, often called the breaker box, functions as the central distribution point for all electrical current entering a home. When this central hub begins producing unusual sounds, it naturally causes concern for homeowners. These panels manage high-voltage electricity. Reduction of the noise impact of electrical substations through a hybrid control strategy based on passive noise barriers and auditory masking. 1980's and later, I subcontracted work for a few small (and one major) companies locating more difficult cases of power line noise. Sound pressure, sometimes written as Lp, refers to the pressure disturbances created as sound waves pass through air. Obstructions in the sound path between the source and receiver affect sound pressure. Sound power, Lw, is the magnitude.
[PDF Version]