Here’s what I learned from Wikipedia tonight. The Guinness Record for highest note sung by a male is known as C#8, which is one note higher than the highest note on a piano. If you want to see the video of the record, see this clip on Youtube.
The highest note by a female is G10, which is three octaves higher than the highest G on a piano, and also well out of the range of human hearing, about 25000Hz. I’d post a video of that, but even if your computer speakers could produce that note it wouldn’t do you a lot of good. Just sit quietly for a couple of seconds and imagine.
For comparison, the highest note I’m able to produce in any ugly fashion is A#6, and the highest Dusty (who’s currently in a community theatre production covering the highest soprano parts) can screech is somewhere around D#6. Two more octaves and she’d best Adam Lopez…
For what it’s worth, the lowest note record is held by a singer named Tim Storm. The record is B-2 (two octaves below piano range), but that’s only 8Hz. 20Hz is the lowest note that a human ear interprets as a tone. We just hear that note as 8 clicks per second.