Why Is There Humming in My Speakers?
By John Papiewski
Updated April 24, 2017
An annoying, low-pitched hum coming from your audio system’s speakers can spoil an otherwise pleasant listening experience. In many cases, the hum is related to the 60-cycle frequency used in household electricity. A variety of electrical problems can cause this hum; some are simple to fix, while others may require repairing or replacing equipment.
Audio cables, especially those placed near electrical power cords, may pick up electrical interference that creates an audible hum in your speakers. In this case, the 60 Hz electrical power in the wire produces faint radio waves; the audio cable acts as an antenna, picking up the interference as a low hum. Fluorescent lights and lamp dimmers also produce this type of radio interference, which your audio cables may pick up as a low-pitched buzzing sound. Turning off nearby dimmers and fluorescent lamps will help you determine the cause of the interference. In addition, if you have power cords laying near audio cables, move them at least two feet away from each other; this may eliminate the speaker hum.
Bad Power Supply
Most audio gear gets its power from a standard household outlet. Inside the equipment, a circuit called a power supply converts the 110-volt alternating current to low-voltage direct current; if the DC signal contains some 60-Hz AC, you will hear it as a hum in the speakers. Normally, components called electrolytic capacitors remove most of the hum, but they can dry out after several years; this occurs frequently in vintage equipment such as tube-type amplifiers. If the hum is particularly loud and you’ve eliminated other possible causes, you may need to fix or replace the power supply.
If you have several components in your audio system, all with their own power cords, ground connection problems may produce hum in the speakers. A phenomenon called “ground loop” can occur when different devices are plugged into various outlets all over a room or building; tiny voltage differences between the outlets cause small amounts of AC to flow in the audio cables between equipment, producing a noise. Problems with the cables themselves, such as broken wires and connectors, can also lead to this situation. Examine the cables for damage and, if possible, power your equipment from a single outlet.
A crack or tear in the woofer’s paper cone may cause a buzzing noise in the speaker, especially during the loud bass parts of music. Unlike the noise from a bad power supply or electrical interference, this sound will be intermittent. If possible, open the speaker cabinets from the front or back and inspect the cones; if you see damage, replace the speaker.
Chicago native John Papiewski has a physics degree and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance."