Japanese table manner

Hi, this is Cherry. I'm from Japan, so I'd like to introduce some Japanese cultures. However, we still have some people from Japan in our class, so I'm going to write about one specific culture, "noise with eating."
One day, I was asked by two classmates about making the noise. They told me they felt ashamed when they have had a bite with their Japanese friend at the restaurant. They really enjoyed sharing their time together before soup was coming to their table. It looked wonderful. At that very moment when they were having that great soup, they heard a horrible noise from very close to them. The noise was actually made by the friend. He(or she) was keeping slurping without noticing their eyes on him. They were so surprised that they couldn't say anything to him about that.
I can understand their feeling because I know slurping is impolite in many countries but not in Japan. It can, rather, be a good manner especially when we have noodle or hot tea. We enjoy them with making "the sound." If it is difficult for you to understand what I'm saying, I recommend you to visit Japanese restaurant(in Convoy st. etc). Yet, it is surely impolite out of Japan, so we should stop doing when we eat something in other countries. I'd like to ask you to tell your friends not to do if they slurp something at public places.