not sure what you mean by RDS...

There also is not an external antenna to make sure is tight on the Tahoe..

Radio Data System

Does this happen when the car is running or does it do it with the key turned to accessory(engine off)?

It happens when the car is running. To be perfectly honest I have never tried to see if it does it while the key is only turned to accessory.

Go out and turn it to accessory and see if you can duplicate the issue again please.

Your radio antenna is in the glass that'* why.

Not to get off topic here, but Nick, you just raised my curiosity. Is the antenna on these sandwiched between the 2 layers of glass, or is it taped to just one side?

I went to take a ride quick to see if I could record it, but of course when you want it to make the sound is doesn't. I'll have to try again, but this time of year I'm not in the Tahoe very much, I am mostly on my bike. Not sure how much the sound would actually help, but I'll try to record it.

Yes, please do try and get a recording of this, also do the accessory test.

I will go try.

It should be part of the defrost panel.