The two main causes of a persistent humming or buzzing are:
- a bad audio cable connected to the amplifier, or
- there is electrical noise being passed through an audio cable into the amplifier.
When audio cables are damaged, they either lose their grounding efficacy or no longer seat properly in the plug. This poor connection creates a low frequency hum and/or buzzing.
It has also been observed that insufficient electrical grounding in buildings can easily travel through audio cables and into an amplifier thereby creating a low frequency hum and/or buzzing.
Bad cables need to be replaced whereas the electrical noise issue might simply require turning down the volume on the amplifier input where the noisy cable is connected.
Step 1: Visually inspect the audio cables for visible damage and ensure they are seated properly. If the noise changes in any way while touching a cable—such as a crackle, pop, or rustling sound—then the cable is likely bad. Unplug that cable to see if the noise goes away. If it does, then you need to replace the audio cable.
Step 2: If there is no visible damage, then unplug each cable one at a time. If the noise goes away, the replace that cable.
Step 3: If the new cable does not solve the issue, then check the volume of the audio source. We have observed grounding issues in classrooms and the noise is simply an amplification of the ground noise.
If a wall control panel is being used, see below. Otherwise, observe what input on the amplifier the cable is connected to and adjust the corresponding volume knob up and down to see if this alters the volume of the noise. If it does, then you need to keep the volume set to a level where noise is no longer audible.
Wall Control Panel: On the wall panel, adjust the volume for the corresponding input where the cable is connected to see if this changes the volume of the buzzing. If it does, then you need to keep the volume set to a level where noise is no longer audible.
Note: you may also adjust the volume on the audio device (such as a laptop), to see if this alters the volume of the buzzing. If it does, then you need to keep the volume set to a level where noise is no longer audible.