I travel some 600 km one-way to the HQ per train every month.
The correct answer is to not book second class tickets, ever, always book "first class quiet zone", and inform offending co-travellers about societally unacceptable behaviour, friendly at first, then increasingly passive-aggressive. There are always some people who are incorrigible ... but Bose N700 noise cancelling headphones also help.
We actually have "quiet zones" in second class here (Netherlands), but it's a bit of a hit-and-miss type of thing. Usually when I've (politely) asked people to stfu I've gotten a reasonable reply ("oh, sorry, didn't realize"), but sometimes not so much, or just say "okay" and continue. Sometimes I don't bother because I'm not in the mood, or the people seem unlikely to be receptive.
1st class tends to be rather expensive. Depending on where you live, even 2nd class can be quite expensive.
The correct answer is to not book second class tickets, ever, always book "first class quiet zone", and inform offending co-travellers about societally unacceptable behaviour, friendly at first, then increasingly passive-aggressive. There are always some people who are incorrigible ... but Bose N700 noise cancelling headphones also help.