Any statement like your example, which is both vague (what exactly do we mean by "friendly"? Can it be measured in any meaningful sense at all, and if so does it have any correlation with noisiness?) and absurdly wide-ranging ("Northern Europeans" covers a wild variety of peoples from the Irish to the Finns, and "Southern Europeans" includes everyone from the Basques to the Montenegrins) is bound of its nature to be untrue.
However: yes, there are differences between specific cultures that are measurable and have been measured - how loudly they tend to talk, how much touching is acceptable, and how much physical space they feel people should keep between each other.
At the link there is a report of a recent study of different nationalities' standards of personal space, which shows how widely they actually do differ. And these real differences can give people quite wrong impressions of other cultures. If you are an Argentinian visiting Norway you will find that the strangers you talk to are keeping more than a foot more of distance between you than you consider normal; to you this behaviour will seem, quite literally, stand-offish, and you will likely go home and tell everyone how cold and unfriendly the Norwegians are, just because of this. (Meanwhile, the Norwegians who met you will say to each other "Aren't Argentinians pushy and in-your-face?")
Edited to add: on average, Americans and Australians speak more loudly than the British and the Japanese do, so if American and Australians visiting Britain or Japan don't moderate their volume they are very likely to be perceived as domineering and "think they own the place".