It seems to be coming from the sea. Would it be anything to do with the windmills in the sea, or I heard there's an oil rig out there. Whatever it is, it was noticeable all day last Saturday from about 6am, but not on Sunday. We only visited Llandudno during those two days so have no idea whether this is normal or not. It just seemed a nuisance as it just went on and on above all other sounds.