My favorite place for singing ever was in a laboratory where I worked. On rotation the techs would have to "wash soil samples" in a room with a piece of equipment called a Fenwick Washer which looked sort of like a big metal fume chamber, with lots of high pressure water hoses and roiling buckets of dirt and water. It was considered a chore by most . I loved it. The echo, the rhythmic pace of the work and all those wonderful negative ions from the rushing water and hoses was incredible. It was so loud it gave you the impression that no one could hear you sing, which wasn't the case. Fortunately everyone else in the lab was very tolerant of my idiosycrisities and my songs.