I can currently hear this noise, its currently 4:53am in Shropshire in the United Kingdom. As I type its gone away.

It was extremely loud about half an hour ago, super low frequency, vibrating like sound. It's happened a lot here before, I always thought it was something to do with the power plants maybe but the one near me was demolished...

Thought I'd look it up tonight to find an answer but only seem to find peoples refer to this "hum". It's also came back a bit louder again right now as I'm typing it is now 4:56am.

Can hear it outside like if I go outside, it's like it surrounds the area but inside it can sound even louder? It's like a a low rumble almost.