It will be from weekly occurrences of very loud, very long fireworks displays, like the one in the video below. We experienced this display right outside our back gate while waiting for the bus. It was very, very loud. The amount of black smoke pouring through the sidewalk from the firecrackers actually had me a bit worried. It's a little hard to see, but there are lots of flowers also on the sidewalk in the middle of the fireworks. The people setting these off were opening a new store and fireworks are typically used in the ceremony whenever you buy something new - a new car, new store, new apartment. I think they are also used frequently at weddings. I've had it explained to me that fireworks are good luck and help to ward off any "evil spirits". An interesting cultural perspective! Although, I would guess that today many people do it because it's fun and awesome to light off fireworks - and any excuse is usually a good one.