My travel partner and I did the same, to see if they would have got the hint, but they did not seem phased.

I feel you, we see these folks mostly in restaurants. They just don't know how to keep their volume down, and they forget that there are countless other people surrounding them.

I blocked my ears and tried to tune them out because I've never wanted to punch someone so badly.

Always carry headphones or earphones when travelling, that's the only solution I know that works. Then you won't have to punch anyone in real life, but do carry on punching them in your mind and imagination, as you listen to some music. 😂