Help! I think we might have termites in the windowsill. Does anyone know anything about this?

In Australia we do not hear termites . Yes they do eat into timber but they tunnel in and they leave a grayish mud from their poo . It may pay you to test the window frame by pushing a sharp nail or small screwdriver into the timber and see if it goes easily in. It takes quite a long time for flying ants to advance in a house yes flying ants are termites but they spread over a large area and if nothing turned up with the renovations taking place I would be looking for house settlement instead of termites for the noise