For three years, we had a young lad in our offices who was playing guitar and singing wherever opportunity lay in the evening. He was a rather large and engaging fellow and a bit brash. Daily, as he went from place to place in the building, he would sing - NOT sotto voce - snippets of songs, with occasional departures into what sounded like scat singing, but may have been mumbling. IT DROVE MOST OF US STARK RAVING MAD! His ego overcame all objections.

I often sing in the car or at home, in the shower, etc. I would never inflict my vocalizing on an unsuspecting general public as I walked through a supermarket or office building as this fellow did.
Our man is now back home on the east coast (US) and accosting a new crowd. By the way, he is not without talent - just a bit insensitive.