From a cultural perspective I'd say ppl can be loud - for various reasons - the foremost being they don't know they're messing up the peace of those around them because this has been the norm from the time since the phone came into being - secondly they think speaking in their native language means less chance of those around understanding or perhaps they don't care - then there are those who do it deliberately - in my culture it is common to talk big so those around know they're listening to a big man/woman talk :)