Quiz time! Guess the noise!
Attached to this post is an audio file. Have a listen and guess the origin.
I recorded this in my rented co-working office space. It's super loud and annoying and has been happening for months.
Engineers have now discovered the source!
Clues:
* I am on the 2nd of 4 floors
* It's intermittent and can happen a few times a day, or 5 times in 5 minutes.
* There is a bathroom nearby
* There are other offices nearby
* It does not come from my office (or me)
Guess!
Bonus clues:
* It can last as long as 15 seconds or as short as 5
* It's been happening since at least August last year, but I have noticed more as I am here more often
It's kind of a grinding hollow metallic noise.
Hand dryer would be my guess as well.
Only thing confusing is the wind down at the end. I'd expect a hand dryer to take less time.
Maybe a saniflo toilet. (as in toilet meets blender)
Is it an old building where pipe diameter could be restricted needing a blender to manage the waste.
Could explain the cadence if there's a toilet block relatively near by or the piping/blender is near(ish) to where you are.
popey
Devlin 
Albert Hickey