Tongues are always a human language.
Peter spoke in Hebrew and the Holy Spirit translated what he said in the minds of the foreigners.
Act 2:1 When the day of Pentecost arrived, they were all together in one place.
Act 2:2 And suddenly there came from heaven a sound like a mighty rushing wind, and it filled the entire house where they were sitting.
Act 2:3 And divided tongues as of fire appeared to them and rested on each one of them.
Act 2:4 And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance.
Act 2:5 Now there were dwelling in Jerusalem Jews, devout men from every nation under heaven.
Act 2:6 And at this sound the multitude came together, and they were bewildered, because each one was hearing them speak in his own language.
Act 2:7 And they were amazed and astonished, saying, "Are not all these who are speaking Galileans?
Act 2:8 And how is it that we hear, each of us in his own native language?
Act 2:9 Parthians and Medes and Elamites and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia,
Act 2:10 Phrygia and Pamphylia, Egypt and the parts of Libya belonging to Cyrene, and visitors from Rome,
Act 2:11 both Jews and proselytes, Cretans and Arabians—we hear them telling in our own tongues the mighty works of God."