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

Further bonus clue.

* The *office* from where the noise comes is a "call-centre".

Final clue (will reveal later today)..

* The device now has a "Do not use" sign on it. :D

@popey I didn’t know faucets ran DNS these days… blimey! So many tech advances
@popey
A shredder?
@robert A popular but incorrect suggestion.
@popey It's gotta be DNS, it is ALWAYS DNS

@popey automatic fan in some rarely used toilet gone bust?

Coffee grinder?

@popey did I guess right :-) ?
@zygoon nobody has has yet guessed the specific item.

@popey ahhhh

What is it!?

The sound reminds me of a weird pipe rattle but my mind also said “cursed DVD drive in some old office printer” and “someone rebooting a SUN workstation in the closet”.

@popey mains (water) water cooler?
@bigcalm @popey yea with you on that one, its got that kinda rubber diaphragm noise, almost pump like
@popey call centre staff screaming into the void?
@popey Oh, then it'll be the screams of the damned.
@popey It'll be their tree chipper, then. Gotta dispose of the non-closers somehow.
@popey that's an oddly specific spelling. Is there a relation to the origin of the noise ?
@frenchguych Which word did I spell weirdly?
@popey it the double quotes and the dash between the words that tricked my weird mine into thinking it was a clue !
@frenchguych Hah! My clues are not that deep :)
@popey then I guess the word *office* between two stars ain't a clue either ?
@popey is it like their version of a sales bell/account deal made kinda thing ?
@popey a sufficiently knackered air hand dryer?

@devlin @popey

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.

@winkleink @devlin I honestly thought it was toilet-related, but I'm told it's not.

@popey @devlin

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.

@winkleink Oh, they know what it is now. I know what it is too. I'm just playing with everyone. :D
@popey
Did you leave one of your Thinkpads against a heating pipe in 'Performance' mode and it randomly does updates. 😀

@devlin @popey

Side note: when doing tech support had a customer who's CRT monitor kept randomly going wobbly. Yes, it was a hand dryer on the other side of the wall interfering with the monitor.

@popey My god sounds like an OLD elevator that DESPERATELY needs servicing!
@feoh It does, but it's not.
@popey Hand dryer attached to the other side of the wall.
@darkling Good guess, and I thought that too. But it's not.
@popey Hmm... second floor, bathroom nearby... is it a water pump?
@darkling The second floor gents is immediately behind my office, and the ladies is above. It's neither of them.
@popey The mention of a bathroom makes me think a vibrating water pipe. Other than that I'd say AC/ventilation unit starting up.
@bit101 It does sound a bit like that.
@popey Before reading the clues, I thought it sounded like a water hammer.
After reading the clues, I think it sounds like a water hammer.
@bigcalm I don't know what a water hammer even is!
What is Water Hammer?

YouTube
@bigcalm @popey not sure if it is a water hammer that I had once, but a thermostatic mixer shower started failing and the water pipes would make a sound not too dissimilar every so often as the pressures from each pipe I think 'had a fight' 🙂
@popey A swarm of bees inside a very echoey duct?
@Jayenkai They didn't say it's *not* that!
@popey water tap in the bathroom when someone opens it?