I have a colleague who sings under their breath while working. It's quite disturbing, even with headphones on. How can I assertively request that they stop doing it without coming across as controlling?
Every suggestion here seems to be jokingly passive aggressive. I'm not sure that's really warranted and the singer may be doing it unconsciously or thinks he is unheard. As a hummer myself, I would prefer someone simply says to me:
"Hey Forklift, sorry to interrupt you, but that singing is a little bit distracting for me. Do you think you could listen to music on your headphones instead?"