Many people have offered the explanation of the Pentecost narrative as a “hearing miracle”, but my take on it is that there was no need for xenoglossy, glossolalia, or any hearing or language miracle - it was simply the apostles speaking in Greek and Aramaic rather than the culturally appropriate Hebrew in this situation.
what follows is a more detailed explanation - it’s a long post so has to be done in three parts, but sums it up rather nicely.
In describing the events of Pentecost with respect to languages/tongues, most people ascribe one of two possibilities: xenoglossia or glossolalia.
I think any way it’s analyzed, we can rule out glossolalia, particularly the modern Pentecostal phenomenon of ‘tongues’; these were clearly real languages the listeners understood; not ecstatic utterances. The description of the event is, at first glance, virtually an ancient ‘textbook example’ of what is known as xenoglossia or xenoglossy – the ability to speak in a REAL language the speaker has in no way, shape, or form ever been exposed to.
Some will argue a miracle of hearing – people HEARD them speaking these languages (but the apostles themselves were not actually speaking them). In postulating a miracle of hearing, what was actually spoken becomes more or less irrelevant.
With respect to what transpired however, a very viable third alternative must be given serious consideration which negates the necessity of a ‘language miracle’ – it simply involves taking a closer look at what languages were actually historically spoken by the Jews, and something called “ecclesiastical diglossia”:
We are told that there were Jews from “every nation under heaven” gathered in Jerusalem. The phrase “every nation under heaven” is an idiomatic expression meaning simply “from all over”. It is analogous to expressions used today such as “all over the word”, or “from everywhere on the planet” – it’s not meant to be taken literally. In fact, the narrative goes on to state specifically where those visiting Jerusalem were from (Acts 2:9-11). It is a listing of geographic places (about 10) and groups of people (about 5). The important thing to note is that NOWHERE does it specifically mention what languages these people spoke; in fact, nowhere in the entire narrative is even one language mentioned by name….not one. This has led many people over the ages to assume that each place referenced in the narrative had its own specific language or languages or that the list is an actual list of languages; it is just naturally assumed that the Diaspora Jews spoke a dozen or so languages which the apostles were not at all familiar with.
If we look at the attendees for this religious holiday in a practical manner however, we can draw a simple conclusion – the masses of people referred to in Acts can be divided into two groups: the “devout Jews” that lived in Judea (Palestine/Israel) – Group 1, and the “devout Jews” from “every nation under heaven”, i.e. the Jews of the Diaspora – Group 2.
By far, the bulk of the people in Jerusalem for Pentecost would have in all likelihood consisted of those from Group 1 since they lived the closest to Jerusalem. Think about it - this is analogous to say having some sort of International Conference of Widget Makers in Boston, MA. The bulk of people attending would come right from Boston and the New England area, with lesser and lesser percentages of attendees coming from further and further away with the smallest percentage coming from abroad. In other words, at Pentecost in Jerusalem, the bulk of the people there would come right from Jerusalem and the surrounding areas. What was the everyday language of Jews from this area at this time period? Simple; Aramaic, but also Greek to a lesser extent.
Turning to the Diaspora (those Jews living outside of Judea), we must make a differentiation between those of the eastern Diaspora and those of the western Diaspora. In addition to the obvious geographic differences, this was a difference in language as well. The people of the western Diaspora lived in areas around the Mediterranean basin; an area which had been very heavily Hellenized for centuries. Places like Pontus, Cappadocia, Pamphylia, etc. had been Greek speaking for centuries. The native language of these western Diaspora Jews was simply Greek. Different countries, yes, but linguistically, all one language. Those Jews of the eastern Diaspora came from places that had never been Hellenized and, as ethnic minorities living in a land either they themselves or their ancestors immigrated to, retained Aramaic as their predominant native language. This is analogous to an ethnic group living in Yourtown, USA – some people in this group will learn and speak English, but amongst themselves, their native language and customs are retained.
In a nutshell, the crowds gathered in Jerusalem for Pentecost would have likely spoken only two languages; Greek and Aramaic. Greek was the language of Jews from the western Diaspora and Aramaic the language of those Jews from the eastern Diaspora and, of course, Judea itself. One must note that absolutely nowhere in the entire narrative does it suggest there was any type of a communication problem to begin with! In Acts 2:14, Peter spoke to the entire crowd in one language and apparently was understood by everyone; I would strongly argue the language he used was Greek; the “English” of its day, understood in varying degrees by everyone in that area of the world.