I'm the bass in our high school a cappella group. Recently we had a performance in our auditorium, and I am almost certain I heard the pitch an octave lower than I was singing. I was singing E3 (164 Hz), and I'm sure I heard E2 (82 Hz).
We were singing with no audio equipment, so it couldn't have been any effects processors.
Do you folks have any idea what I could have experienced?