DVD player noise

I've been lurking around for a day or two looking for the answer to my noise question.  I haven't found one that fits my situation (or I just don't know enough to have recognized one of the other posts as addressing my problem... but I digress).

I put a Sony DreamSystem in my 2000 Mazda MPV using an Audiovox FMM100 fm modulator.  System works, looks, sounds great!  But I am getting some noise when the DVD is at a quiet passage (or on one of the menus).  I recognize the noise as a blipping/squeaking kind of noise that the DVD player makes (when you hold your ear close to a dvd/cd player) only  the noise is being amplified over the speakers.  I had this same problem many years ago with a portable CD player coupled with a Cassette Adapter.  I hope that describes the noise well enough.

I am not running any amplifiers.  The FM Modulator is grounded to the chassis at a point where a metal dash support beam is bolted into the floorboard.  The DVD player is grounded on another bolt about 2 inches away.  The FM modulator is about 12 inches from the nearest power wire to the DVD player.  The FM modulator has a built in noise suppressor.

The noise is most notable when the engine is off (guess that would be obvious, eh?)  I am not getting any ignition/alternator noise at all.  Volume levels between an FM station and the FM modulator are fairly close... the FM modulator may be 5-10 db quiter than an FM channel. 

What do you folks suggest?

Bengoshi2000