If you're singing in the shower, so you are in fact there
You would still hear yourself, so yes.
Unless there is some kind of existential crisis going on here in addition, you qualify as someone and are therefore there to observe the singing
Unless you were deaf, in which case it cannot be properly determined whether or not you were singing at all.
You could be screeching. Or speaking.
Now if there's a partially broken radio in your shower with only a 50% chance of working, and you are not in the room, according to Schrodinger the radio is both playing music and being silent. It is the act of you returning to the room and observing the radio that actually decides an outcome.
I love applying quantum physics to unrelated situations.
True story. Thank you Schrodinger's Law.
That poor poor cat...
This is such a heated discussion. xD
Now you need to start asking the real questions