A few years ago I spent a night in a youth hostel. The bed was really uncomfortable and I just couldn't get to sleep. With nothing else to do (it was too dark to read) I pulled my boxer shorts down, rolled onto my side, facing the wall. I touched and caressed my penis and it stiffened. I wrapped my hand around my growing erection and stroked slowly, trying to keep quiet. There were about four other people in the room but I didn't really mind if they could tell what I was doing (after all everyone masturbates) but I still wanted to be discrete.
I was taking my time, going slowly and really enjoying the sensations when I heard a sudden 'Uh!' from one of the other guests (who was a teenager). I realised that he hadn't been able to keep his hands off himself any more than I could, the noise was the involuntary grunt as he climaxed. The thought that someone in the same room had just masturbated to orgasm made me hot and I stroked myself to an intense orgasm of my own, spurting onto the sheets.
I wonder if anyone heard me as I came.