I found these two articles by Robert Zerhusen very helpful on the study of speaking in tongues. He gives compelling arguments to believe that tongues are known human languages in both Acts 2 and 1 Corinthians 14, and not ecstatic utterances. They were published by the Alliance of Confessing Evangelicals:
Perhaps a great question to ask before and while you read is, “Who ever said that tongues has to be a miraculous gift?” The Bible certainly say that, or really even imply it.
At the end of the day, this debate doesn’t make a lot of difference, as it’s not an essential thing. However, we are called to know the Scriptures and study them. Wherever you are at on this issue, I hope these articles are beneficial to you.