Orthodox Shul Decorum
Here is the real reason why it is generally much noisier in an
Orthodox shul than in others.
When you go to a stranger's house for the first time, you are
generally respectful and quit. You sit properly, you don't speak
till spoken to, you focus on the host rather than other company
you're there with. On the other hand, when you go over to your best
friend's house, you raid the refrigerator, you shmooze with other
friends that hang out there, you put your feet up. In short, you are
comfortable and not in awe. This applies even if your friend is a
powerful person in the community.
Something similar happens in synagogues. If you don't go to shul
that often, as with Jews who only go on Shabbat, you are proper and
polite. When you're there several times a week, as do many of the
Orthodox, this must be your friend and you kick back, relax with
friends, talk with them, etc. thus the difference in decorum.