Why is my speaker buzzing? Is it a ground loop? How can I fix it?

4 Effective Ways to Eliminate Ground Loop Hums | SC&T

Ebtech Hum X Ground Line Voltage Filter,Black

DigitalLife 3.5mm Audio Ground Loop Noise Isolator - Hum Eliminator, GI35-A

XLR Ground Loop Isolator Hum Eliminator for Home Stereo System/Speaker/Car Audio/Car Kit/Audio Player (Eliminate The Buzzing Noise) (XLR-Dual Channel Stereo)

Earthquake Sound GLI-200 Hum and Buzz Kleaner 600 Ohm RCA in/Out Ground Loop Isolator

2 Packs Ground Loop Noise Isolator for Car Audio/Home Stereo System, Ground Loop Isolator with 3.5mm Audio Cable