This rule is widely known but still misunderstood. If you do not slurp you are not being rude. If you do slurp, it's totally normal but does not necessarily indicate that you think the food is especially delicious. Basically, you can slurp all you want or you can eat your ramen in silence — it’s all-good either way. But slurping does help the noodles act as a vessel for better transporting the soup from the bowl to your mouth. It also cools the noodles down as you inhale the goodness. Above all, slurping lets you enjoy your noodles quickly and freely without having to worry about whether you are eating like a pig. You don't need to overthink it; there is no rude way to eat ramen. If you want to drink the soup straight from the bowl, by all means indulge. Just enjoy the bowl and you are doing it right. And don't worry if you can't finish all of the soup.