I have the same whistle on my 15 FLTRUSE. Happens around 60 mph. Taking it in for the 1K service tomorrow. Will have them look at that and the audio system - speed volume control isn't working.
Speed volume control is one of many things not working on your radio / navigation unit. Dealer can on;y document the issue and send the complaint to HD.
The soft ware had had two updates since I got my bike, and neither have fixed that issue. The newest version is 1.18.2.
Other issues are auto dimming, not going bright again.
Text notification not working
Text auto reply not working
Time zone wrong for East TN
Front to rear fade
Head set speakers not working for phone
And many more...
Not bad for a head unit they have been using for 16 months, still can't get it right