A few years ago there was reportedly a persistent hum where I live in Surbiton, Surrey, UK. There was a thread on a residents message board[0] that escalated only as far as the local rag, and the council issuing noise diaries[1]. What disappointed me the most is that despite living in almost the epicentre of where the complaints were made, I never heard a damn thing.

[0] https://surbiton.com/forum/surbiton-background-hummmmmmmm [1] http://www.yourlocalguardian.co.uk/news/10999038.Mysterious_...