Noisy opponent -- your responsibility?

Question

My opponent seemed to me (then a teenager) an elderly guy but I think he was just in his 50s or 60s.

Anyway, he literally was audibly and somewhat loudly talking to himself, saying, "If I go there, then he goes there... but then... and I got him!" -- even in a casual game, much less in a large and crowded tournament, this would not be acceptable.

He was older than my dad and he was losing anyway so I did not say anything. Then another player, also eccentric looking and acting (I knew of this guy, a "B" player who called himself a pro -- almost impossible because if he did manage to win a class prize, he would move up to "A" anyway: I think only a GM, in those days before the Internet allowed pretty girls and articulate FIDE masters etc. to make money from Youtube) came to our board and, fairly loudly himself, asked, "Is there something wrong with you??"

My opponent looked somewhat offended but said nothing and then significantly did shut up and I wonder if the whole thing was some sort of act trying to distract me.

But the guy who had chastised him then stared accusingly at me before walking off, as if to say, "Why are you making me do this?"

I am pretty sure I had no special responsibility -- I doubt if this specific thing is mentioned. I am sure there is a "silence" rule but I doubt that the opponent is supposed to be the first line of defense.

However, maybe informally I should have been the first to gently shush him.

This does not come up much in adult events (never played in a kids-only event).

Answer 1

Noisy opponent -- your responsibility?

Of course not!

1. You may be deaf and totally unaware.
2. You may also be playing somebody with mental health issues and you choose to show some understanding and make allowances.

You are the one to decide if you are unduly disturbed by your opponent (or anybody else's opponent, for that matter) and it is entirely up to you to decide if you want to request silence from your opponent or to take it further with the arbiter.

Answer 2

Whether or not you decide to complain to the Arbiter is indead up to you (don't forget to pause your clock!).

It is important to note, however, that the Arbiter or another player in the Tournament Hall can autonomously decide to complain or take action.
Disturbing your opponent is indeed forbidden, as stated in Articles 11.5 and 11.6 of the FIDE Laws of Chess:

11.5 It is forbidden to distract or annoy the opponent in any manner whatsoever. This includes unreasonable claims, unreasonable offers of a draw or the introduction of a source of noise into the playing area.

11.6 Infraction of any part of Articles 11.1 – 11.5 shall lead to penalties in accordance with Article 12.9.

Which leads to Article 12.9 that states the penalty options of the Arbiter (anything from a simple warning to the complete expulsion of the Tournament).
Also, article 12.2 mentions that the Arbiter must respectively ensure 'that players are not disturbed'.

Conclusion: both your adversary and the interfering player should have been penalized by the Arbiter. If the Arbiter didn't do it (because perhaps he didn't see it), your (noisy) adversary could have asked him to do it. Additionally, the interfering player should have asked the Arbiter to penalize your adversary instead of disturbing your game. You, as a young player, were perhaps to shy to complain, but the interfering player (or the Arbiter) should've done it in your place.

Personally, I tend to observe adversaries of younger players more rigorously than adults since those kind of 'mind tricks' tend to occur rather regularly. In large tournaments that's unfortunately not always possible. But the focus of the Arbiter should've been to prevent the entire situation in the first place (with perhaps only a warning for your adversary).

If I were the Arbiter then, I would have penalized both players with a time penalty and a clear warning. However, I am well aware that these situations are influenced when e.g. it all happened in an internal club competition or the Arbiter and the offender(s) know each other personally etc.