The intercom circuit should be reasonably interference or static free. If it's also in the music playback, then yes, I'd say a bad ground circuit on the system itself. If just the i/c, is it in both headsets? If it's just one set, then I'd point a finger at the headset itself, or the connector. If it's in both, then there's a fault 'somewhere'. If the sensitivity (squelch) is set to mostly eliminate road and wind interference, it's likely internal (system harness). Give us some more info if you can, maybe someone's come across this before.
EC in Knoxville, Tenn. does a service that claims to correct this very problem and it has to do w/insuring the grounds are in deed "working" as they should.
I believe one of the main grounds can only be accessed by removing the gas tank!
I have a 2006 GL1800 and I use in-ear-canal ear-buds from PlugUp and the noise is awful. The Cruise control makes a terrible noise, the intercomm is noisy (my Radar detector is connected though intercom, there are no mics). I installed a ground loop isolator on the aux power in the left pocket (this powers the GPS/XM Radio) (from EC), an in-line filter (from EC) and still there is significant noise particularly from the cruise motor. I bought an inline filter from Radio Shack on a recommendation from this forum. It swaps volume for noise. Best solution so far.
I'd really like to get rid of the noise without all the gadgets, particularly the in-line filter since it cuts volume.