"As we have mentioned in recent articles, by “speaking in tongues” we do not refer to the modern charismatic practice of random mumblings, but to the Biblical reality of preaching the Gospel in multiple languages through the special inspiration and action of the Holy Spirit. By speaking in tongues, the apostles were moved literally to speak many languages of which they had no previous knowledge.
At the Pentecost after the first Easter, the apostles were moved by the Holy Spirit to speak in tongues – and this was not a miracle in the hearing of the audience, but in the preaching of the apostles. When the crowd in Jerusalem states that we have heard them speak in our own tongues, we are not to think that the apostles spoke only one language (Aramaic) and that this single language was transformed into many languages according to the needs of the hearers. Rather, it is clear that they began to speak diverse tongues."
I do not believe the apostles just rambled on in delirium, but had to use different languages because of the foreign audience they encountered.
So today's 'speaking in tongues' is yet another misnomer used by some Christians to communicate with God, when simple prayer would suffice in whatever language that person spoke as God understands all.