Scriptures do not support tongues being defined as gibberish or some unintelligent garbled sound that cannot be understood.
The tongue that is spoken of is a language, a foreign language, not a garbled sound that is not known. There were gathered in Jerusalem on the day of Pentecost people from about 16 different nations, who spoke over ten different languages. During this period in history the world spoke mostly Greek, however, you will notice in Acts 2:11, that the people heard the apostles speaking in their own language. As the result of the people hearing in their own language, they people were amazed and perplexed.
In the records in 1 Corinthians, the obvious giving of languages (tongues) was a working of the Holy Spirit in the same sense that workings of miracles, prophecies, discerning of spirits and the interpretation of tongues.
Paul, the author of 1 Corinthians, says that the greater gift, rather than speaking in tongues, is love. He also says that this gift of speaking in tongues (languages) is to be in an orderly fashion, and only then if there is someone there to interpret. Also he says that the speaking in tongues is a sign to those who are unbelievers.
If someone comes into your assembly and you are speaking a lot of garbled sounds that cannot be understood that the unbeliever will not understand.
1 Corinthians 13:8, Paul says that prophecies and speaking in tongues will cease and love will remain.
From a careful reading the various texts where the speaking in tongues is mentioned it is obvious that whatever it is one can and does understand.
The speaking in tongues in all these references is a foreign language and not gibberish.
Mark 16:17
17 And these signs shall accompany them that believe: in my name shall they cast out demons; they shall speak with new tongues;
ASV
Acts 2:3-4
3 And there appeared unto them tongues parting asunder, like as of fire; and it sat upon each one of them.
4 And they were all filled with the Holy Spirit, and began to speak with other tongues, as the Spirit gave them utterance. ASV
Acts 2:11-12
11 Cretans and Arabians, we hear them speaking in our tongues the mighty works of God.
12 And they were all amazed, and were perplexed, saying one to another, What meaneth this? ASV
Acts 10:46
46 For they heard them speak with tongues, and magnify God. Then answered Peter,
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Acts 19:6
6 And when Paul had laid his hands upon them, the Holy Spirit came on them; and they spake with tongues, and prophesied.
ASV
1 Corinthians 12:10
10 and to another workings of miracles; and to another prophecy; and to another discernings of spirits; to another (divers) kinds of tongues; and to another the interpretation of tongues:
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1 Corinthians 12:28-13:1
28 And God hath set some in the church, first apostles, secondly prophets, thirdly teachers, then miracles, then gifts of healings, helps, governments, (divers) kinds of tongues.
29 Are all apostles? are all prophets? are all teachers? are all (workers of) miracles?
30 have all gifts of healings? do all speak with tongues? do all interpret?
31 But desire earnestly the greater gifts. And moreover a most excellent way show I unto you.
1 Corinthians 13:1
13:1 If I speak with the tongues of men and of angels, but have not love, I am become sounding brass, or a clanging cymbal.
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1 Corinthians 13:8
8 Love never faileth: but whether (there be) prophecies, they shall be done away; whether (there be) tongues, they shall cease; whether (there be) knowledge, it shall be done away.
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1 Corinthians 14:2-9
2 For he that speaketh in a tongue speaketh not unto men, but unto God; for no man understandeth; but in the spirit he speaketh mysteries.
3 But he that prophesieth speaketh unto men edification, and exhortation, and consolation.
4 He that speaketh in a tongue edifieth himself; but he that prophesieth edifieth the church.
5 Now I would have you all speak with tongues, but rather that ye should prophesy: and greater is he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying.
6 But now, brethren, if I come unto you speaking with tongues, what shall I profit you, unless I speak to you either by way of revelation, or of knowledge, or of prophesying, or of teaching?
7 Even things without life, giving a voice, whether pipe or harp, if they give not a distinction in the sounds, how shall it be known what is piped or harped?
8 For if the trumpet give an uncertain voice, who shall prepare himself for war?
9 So also ye, unless ye utter by the tongue speech easy to understood, how shall it be known what is spoken? for ye will be speaking into the air.
ASV
1 Corinthians 14:13-14 3 Wherefore let him that speaketh in a tongue pray that he may interpret. 14 For if I pray in a tongue, my spirit prayeth, but my understanding is unfruitful. ASV
1 Corinthians 14:18-19
18 I thank God, I speak with tongues more than you all:
19 howbeit in the church I had rather speak five words with my understanding, that I might instruct others also, than ten thousand words in a tongue.
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1 Corinthians 14:22-29
22 Wherefore tongues are for a sign, not to them that believe, but to the unbelieving: but prophesying (is for a sign), not to the unbelieving, but to them that believe.
23 If therefore the whole church be assembled together and all speak with tongues, and there come in men unlearned or unbelieving, will they not say that ye are mad?
24 But if all prophesy, and there come in one unbelieving or unlearned, he is reproved by all, he is judged by all;
25 the secrets of his heart are made manifest; and so he will fall down on his face and worship God, declaring that God is among you indeed.
26 What is it then, brethren? When ye come together, each one hath a psalm, hath a teaching, hath a revelation, hath a tongue, hath an interpretation. Let all things be done unto edifying.
27 If any man speaketh in a tongue, (let it be) by two, or at the most three, and (that) in turn; and let one interpret:
28 but if there be no interpreter, let him keep silence in the church; and let him speak to himself, and to God. American Standard Version
From a reading of the above scriptures one will see that speaking in tongues was a foreign language that had a miraculous application, but was limited to the early beginning of the church ( 1 Corinthians 13:8). The apostle Paul said that they would cease along with the other miracles of that time.
On the day of Pentecost, it is observed that the people heard the apostles speaking a language in their own tongue in which they were born.