"but as has already been mentioned, always use earphones and keep them turned down, especially if you're sitting right next to another passenger."
Which, really, is just common courtesy on any form of public transportation, be it Amtrak or a city bus.
In fact, like Amtrak, headphone use is mandated in C-Tran bylaws. Now, if only they would do something about all those damned cell phone yakkers on the #4, #37 and #80 routes during c/rush hour...