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.
Ah, so the facilities team are also stumped.
It sounds like something spinning fast.
Does it seem to come from above, below, to the side of where you are.
As in ceiling, floor or walls.
Id ceiling then aircon/air ducting is a possibility.
If walls the water piping.
If floor it depends if it's a raised floor and what kind of stuff is put under there.
popey
Devlin 
Albert Hickey