- Turn off subwoofers and see if noise is coming from the center
- Turn on one subwoofer at a time and see when the noise starts
- Unplug/Replug the subwoofer cables, try a different cable
- Is there a PC on a UPS or something plugged into the same line. Turn that off
etc. etc, (narrow down on what’s creating the noise by process of elimination)
If the sound shows up only on the center channel and subs (not the fronts??), i am also inclined to believe that it may be something with the av processor/receiver. Check all cable connections, check for sht failing cables, make sure everything’s plugged in where it’s supposed to be, etc.