I have the base 7 speaker system but it has been upgraded with new speakers all around (minus center) and a JL RD900/5 and LC5i Pro.

I narrowed it down to the USB C (and maybe the USB A) port by the following troubleshooting steps:
- Routed audio to the center channel only, noise still happens
- Tried two different cables, noise still happens
- Switched to BT, noise stops
With those steps above im 95% sure my install has nothing to due with this sound.

Has anyone run across this issue? It's the same sound you would hear if speaker wires are loose. It's not the super loud noise i've seen posted about elsewhere , it's only loud enough to be annoying. The radio functions when this happens.

Side question: Is it normal for the rear speakers to go quiet and get very distorted when fading all the way to rear? They sound normal otherwise.

 

Welcome to the forum.

 

Yes I have same issue with same 7 speaker system. I’ve found that using an original apple usb cable for my iPhone helps compared to aftermarket or stream through Bluetooth and it goes away. Fairly certain it’s the usb port. I completely bypass the head unit now with coaxial directly into DSP