It's funny the subject has moved to the noise instead of the light because about the same time today as your weird experience I was sitting here at the PC listening to a noise outside that went on and on for at least an hour. I eventually got up to go see, expecting to see a huge truck or something idling at the side of the road. There was no truck there.
I THINK it was the council strimming the shrubs on the footpath behind our houses, but it was torrential rain at the time so I'm just not sure. Just
thought I'd throw that in there. Next time I hear a strange noise I'm going to see exactly what's making it.