Woken from sleep by a loud vibrating in the house – initially thought it was a washing machine but it got louder and deeper. got up to look out the window as it appeared to be coming from outside and thought it might be a low flying plane as it initially sounded a bit like a jet engine (but at 2:30am this seemed unusual). opened the window and it felt like the whole sky was humming/vibrating. tried to record it on my phone but the sound was too low a frequency and was much more of a vibration. very oppressive and made me feel very alert – lasted for around 20 minutes. spoke to someone about it a few weeks later who also heard it but from 30 miles away (northwards)!