Honking on Donegall Rd?

Hi all. I live on Donegall Rd just near the EuroSpar. Since moving in (it’s been months) I have noticed that many people honk. Not particularly at each other like normal traffic, I mean honking a tune each time they pass a certain point. Is there a reason for this? A cultural or political thing? Or just a complete coincidence? It happens during rush hour, middle of the night, throughout the day.