At the very bottom of its working voltage range (4ishV), it was still audible...not loud, but if it were the only thing in the room, you'd notice it.

Can't get better/official numbers until I get a new DMM :-/ (or a new fuse, but I think it's time I get a new DMM anyway)

EDIT: just realized that made no sense above....lol. Anyway, with the thunderstorm, audio tests are useless....and if I wanted to plot the U1A vs. the San Ace, I'll need to get my DMM working anyway.