3 bikes I know in my small group ('08 Ultra, '08 EG Classic, '10 Roadglide ; all with TC96) had the following symptom:
bike idle in neutral: nothing unusual
Pull in the clutch: nothing unusual
Click it into first gear: whirring noise that some also called a rattle - I called it a whirring noise.

Diagnosis, on all 3, inner primary bearing and race. After repair, all was good again. One of the 3 was mine.

You stated you hear the noise when you roll up to a stop with clutch pulled in and idle rpm - I assume you're in gear when this happens so similar to our experience.

 

I would agree. If you are in gear and your inner primary is going bad, you will hear whirring noises. It will gradually get louder and happen not just when the clutch is pulled in. Have a tech check it out, they will recognize it pretty quick if that is what it is.

 

My rattle was that the rear turn signals were loose.

 

Exhaust heat shield clamps fail. On the front heat shield the spot weld failed where the clamp attaches to the heat shield and it buzzed for quite some time before I finally located it.

 

Yes, check the heat shields.

 

I had my 2016 RGU in the shop for the clutch recall. I told them about the ringing sound and they could hear it and checked it out. No answers at this time. They did not think it was the primary or the compensator. I think it sounds like clutch plates rattling. It goes away with the clutch pulled in. The sound comes and goes but is loud in 4th gear. Only happens when the bike is warmed up. The rattle at idle, in neutral, gets louder with rpm rise. I only have about 5500 miles on the bike and the sound did not start until I was at about 4000 miles. Heat shrouds are tight, no problems with horn or air cleaner. There is play with the foot brake and shifter but no rattle from those. Floor boards seem okay. I think I will be chasing this one for a while.