These phrases have the same meaning, but I would consider the first to be more polite. I have always been told it is better manners to put 'please' at the beginning of the sentence or before the verb rather than at the end. (Please eat your food vs Eat your food, please!) This could vary, however. How I would ask people to calm down (said in a respectful and unabrasive tone) would be: "If possible, could you please speak a bit softer? I need to study/ do something. Thanks so much!"