Ground loop isolator

Your link does not work.
What is this supposed to accomplish anyway ?

 

Usually it's an in-line noise isolation filter (sometimes called transformer.)

About $10 if you need one.
Almost never needed on OEM audio.

 

If you have wired your own music system so that you have grounding issues, this isolater solves them.

 

That's what I thought.

And it sounds SO much fancier than "noise filter" !!

And a ground loop is not the same as the lack of sufficient grounds.

 

Who is that question aimed at......me ??

True ground loops usually aren't a problem with mobile audio.
But relying on the car body to provide a ground can introduce noise.
So can having excessively long ground runs of too small a gauge of wire.
The problem is an insufficient ground, not a loop.
Using a single point "ground" is useful in both situations though; in the case of a mobil installation, the battery or the frame near the starter.

And finally, if it is the phone itself that creates the noise while charging and it gets into the audio output INSIDE THE PHONE, then there isn't much you can do about that......because it is not a grounding problem.

 

deleted by author

 

Kill the noise at the source!!

The problem isn't the audio system, it's the phone charger.
OK....so the audio system in the Prius is sub-par, but the SOURCE of the noise is the charger.
Some phone chargers cost $30, and others you can get at Harbor Freight or a Walmart Checkout aisle for $5, and not all of the difference is in the amount of power that they deliver.

So....
Since you probably don't have an o-scope handy what I would do is borrow several chargers from friends to see if one of them is substantially quieter than others.
My beloved company gave me a Belkin charger when they "upgraded" [sic] me from one Apple product to another, and I noticed that it was quieter than the 3/$10 units that they were passing out with the previous phones.

Some more details about your specific setup are needed for a more definitive diagnosis...