Making sounds while eating is bad manner in Western culture. In Japan, it’s not always so. Particularly when you eat noodles or mugitoro rice, you are supposed to make sounds while eating. Those are casual food, therefore they should be eaten with casual manners. Expensive restaurants don’t serve these kind of food, anyway.
Sometimes elegant women eat noodles or mugitoro rice without making sounds. It doesn’t look natural to me when I don’t hear anything while someone is eating soupy noodles or slippery food using chopsticks. When you eat those food, just enjoy eating without worrying about making sounds. I bet it tastes better.