While we're knee-deep into the toilet conversation, you make an interesting observation. I'm originally from France and have lived in California for over 11 years but, to this day, I'm still astonished at how little embarrassment there is in American toilets (my experience is limited to the mens rooms) as far as unpleasant noise goes. It is obviously a fact of life but, where I come from, denial is king in that department.

My theory is that it's because American public toilets are usually made of 2 thin, low separation walls and a door with sometimes wide gaps which makes it almost inevitable to share the entire experience with everybody in the room.

Still not used to it...

I think it's just cultural: American men are not expected to be discreet or embarrassed in "practical" all-male environments such as locker rooms and public toilets. A loud belch or other powerful, resounding emanation signals manliness... and it was funny when you were 7, it's still a bit funny now.

"off-screen sounds" as they're called in entertainment, meaning sounds that have no visual cue to explain their existence, ignite a fleet startle response from ear to brain. The science behind the funny and the awkwardness of farting or belching. When expressed loudly, might not even be that far from the roar of a large carnivore.

a bit funny? Liar. It's hilarious! Who cannot but smile at a cubicle wall rattler, whether your own or someone elses?

For working class white American men, that is not limited to public restrooms. They're doing it at home too and laughing about it to their wives/girlfriends/kids - who probably call them disgusting to which they laugh even more.

People with more class and manners tend toward the French way of doing it.

You mean people who are snobs tend toward the French way where as people who are fun and warm hearted have no problem laughing at farts.

I would much rather be with a person that thinks farts are funny then one who doesn't. To each their own.

Funny or not (I don't think I'm any different from the natives in that regard), that doesn't explain why they would find it perfectly reasonable to share the joy in public where "fun" is certainly not the aim.

Those are hardly 'facts' as much as they are anecdata. From the working class families I grew up in and around, I could assert with just as much first hand data how baseless your assertions are.

This is an excellent example of circular reasoning, as I see it.

"More mannered people are more mannered because they do not do things I consider ill-mannered."

A fart is a fart. Go to southeast Asia, it's still just a fart that people laugh at. Go to Europe and fart and now leave a bad impressions due to culture? I see which is the optimal setup for practicality and sanity.

I don't think that "class" and "manners" are very healthy in this case. Farting is very natural and happens consistently. You shouldn't have to hide that or be embarrassed about it.

That said, I tend to look for bathrooms to relieve myself privately.

    2) An artificial sound to overlay embarrassing 
    farting sounds: Without this feature, it was 
    common for Japanese women to constantly use 
    the flush in order to create a louder sound. 
    This was obviously a huge waste water.

Was this an issue because Japanese walls are thinner? Or homes smaller? Farting isn't considered particularly appetizing here either but I don't remember a single time this has been an issue (or ever hearing someone farting from outside the bathroom).

The flushing is designed to cover up 'all' sounds. There's a lot of weird fetishes and taboos and hangups people have out here, so I wouldn't read too deeply into it. Diet is probably not a factor.

The otohime is a huge water saver, though.