OK, 120 Galilaeans suddenly start acting up a scene talking about some ghost or something with their hair on fire, some think they're drunk. This was spread eveywhere word of mouth and here comes all kinds of people talking about hearing them in their own language. Wait, what's that? Why is that a big deal you say? This place is full of out of towners and it's not that unusual to be multi-lingual. Wait...we're hearing and understanding what they are saying even though we know the person standing next to us and over there is of a language that neither of us speak. Now that's news! Three thousand people were converted that day and it wasn't because the 120 knew a few different languages.
NOT UNUSUAL?!?!Good grief.
And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? And how hear we every man in our own tongue, wherein we were born? Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia, Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
1. Parthian
2. Medean
3. Elamite
4. Mesopotamian
5. Cappadocian
6. Judean Hebrew
7. Pontian
8. Asian
9. Phrygian
10. Pamphylian
11. Egyptian
12. Libyan
13. Cyrenian
14. Latin
15. Cretan
16. Arabic
Luke identifies sixteen different languages or distinct local dialects over which the Apostles gained Power that day, and that's just the listing which he cared to mention.
Rustic aramaic-speaking Galilean fishermen do not speak 16 different languages. It would not only be unusual, it would be unheard-of.
It would be a Miracle.
It would be the gift of Power over Foreign Tongues.
I think you are overread these verses. As a Calvinist I don't find it hard at all to believe that 3000 were converted. Same scene, different men; and they thought these people were drunk. God poured out His Spirit on some and not on others. As many as were appointed unto eternal life, believed (just like it says further on in Acts).
There is also no reason to read the story as saying that the disciples spoke in some angelic language which no one knew but it was still heard in the language of the Parthians or the Medes or the [etc.]
I'll post further discussion of this when I get a chance.