I think the idea was the noise would make people come out of their houses and see what was happeningFine detective work my good man.
So the noise was a secret City of Culture event attracting 3000 people to an event right near where I live that I knew nothing about.
I suppose there is some logic in not telling anyone about it...after all 13000 people turned up at 9 burger vans in Trinity square.....
quite cool really