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!