"Brian Gaff" wrote in
:

Even toilet cistern can have weird oscillator issues. I was in a
block of flats and used the toilet as the water was close to cut of it
sounded a bit like a badly played penny whistle. Luckily not my
concern, but I did wonder if the flat next door to the visitors toilet
might be occupied by the deafest member of the community!
Brian


Some people tolerate stuff and do not recognise such noises as an
opportunity to apply a fix.