God knows how we each speak, and hear, in our own language dialects of birth. That's what the various peoples on Pentecost heard, in their own dialects of their home languages, when the Apostles spoke on Pentecost. That... is... the evidence of the true cloven tongue of Acts 2.
So yes, each person, with their own hearing... understood. And that was about known languages of the world, even dialects of those languages which is even more specific! That is why many wondered there, because they knew the Apostles were Hebrews, so how did they learn their own dialects so well? It would have required years for one to live in an area to learn the dialect/slang of just one language. Yet that is how ACCURATE The Holy Spirit was in translating each language of each person's country that was present. And that is the true evidence of the cloven tongue of Pentecost.
But that is not all; there will be a certain event that is to occur during the coming time of 'great tribulation" our Lord Jesus taught, and that is when some in Christ will be delivered up to give a Testimony by The Holy Spirit, to all nations. That is actually the event Peter spoke of when quoting from Joel 2. When Peter said, "this is that" which the prophet Joel spoke about, it means Pentecost was an 'example' of that still future event.