In-Between Reflection: U-District Serenade?

I have always sung to myself, under my breath, as I'm walking around. I've been doing it so long that I generally just take for granted that nobody can hear me. I wonder if I was audible this evening. A couple people looked back at me and laughed. A quick scan revealed that my fly was zipped, and there was no toilet paper attached to my boots... so I'm guessing probably I was audible.