John Calvin Commentary Acts 22:2

"And when they heard that he spake unto them in the Hebrew language, they were the more quiet: and he saith," — Acts 22:2 (ASV)

That he spake Hebrew. This is indeed a usual thing, that when people who speak different languages are together, we listen more willingly to those who speak our own language; however, the Jews were moved by another particular cause, because they imagined that Paul was alienated from his own people, so that he even hated their tongue, or that he was some rogue who had not even learned the speech of the nation from which he said he came. Now, as soon as they heard their own language, they began to have some better hope.

Furthermore, it is uncertain whether Paul spoke in the Hebrew or in the Syrian tongue; for we know that the speech of the Jews had become corrupt and degenerate after their exile, since their language had absorbed much from the Chaldeans and Syrians. For my own part, I think that because he spoke to the common people as well as to the elders, he used the common speech that was usual at that time.