i was an exchange student in japan for a summer and when i was there i noticed that people chewed with mouths open and slurped soup/noodles. i was told by the family i was staying with that the more noise you made as you ate, the more you showed the cook you liked the food. it was common there and after a little while, it was no big deal.
for a few weeks after i came home my family would give me all kinds of looks when we ate dinner and asked if i was 'enjoying my food' because i was being loud and chewing with my mouth open.
different strokes for different folks.