If you are talking about in today’s etiquette, Apparently it is rude. But I do not agree with that etiquette if the question asks about that. Not everyone is going to intentionally make loud noises and some farts are uncontrollable. Like this is like trying to get someone to not snore when they sleep. Maybe you can try methods before you sleep, But when you are unconscious and sleeping, How are you going to get them to not snore? And how are you just going to say that’s rude?