There are 3 instances when Prophet Paul was narrating about the vision of JESUS was talking to him in Hebrew but his men did not understand the voice but heard the sound.
Etheridge Translation from Aramaic Text
Acts 9:7 - And the men who went with him in the way stood astonished, because the voice alone they heard, but a man was not seen by them.
Acts 22:9 - And the men who were with me saw the light, but the voice they understood (Lit. "heard") not which spake with me.
Acts 26:14 - And we fell all of us upon the earth; and I heard (understood) a voice that said to me in Hebrew, Shaol, Shaol, why persecutest thou me? It is hard to thee to kick against the pricks !
Greek word G191 "akouo" in Acts 22:9 can mean "hear, be noised, be reported, understand". And the Greek word G5456 "phone" means "noise, voice, sound, saying or language".
There is no contradiction between Acts 9:7 and Acts 22:9 because the Greek word G191 "akouo" can either mean "understood or heard" in this context; the choice of word depends on the context of the message as in Acts 26:14 the voice can also mean "language".
In Aramaic the word for "heard" can also mean "obeyed" in Acts 22:9.
Acts 26:23 - that the Meshiha should suffer, and should be the chief of the resurrection from the house of the dead, and should preach light to the people and to the nations.
Witness 1 -- The Disciple Ananias was called by God to pray for Saul's recovery of his sight:
Acts 9:10 - Now there was in Damascus a disciple named An-a-niÆas, and the LORD said to him in a vision, An-a-niÆas. And he said, Behold, I am here, my LORD.
Acts 9:15 - But the LORD said to him, Arise and go: he is the agent whom I have chosen for myself to carry my name to the Gentiles and kings, and the children of Israel:
Aramaic- Etheridge Translation:
Act 26:24 AND as Paulos was thus making defence, Festos cried with a high voice, "Thou art mad, Paulos; much learning [Or, many books.] hath made thee mad!"
Act 26:25 Paulos said to him, "I am not mad, victorious Festos, but words of truth and righteousness I speak."
Act 26:26 And king Agripos also, especially, knoweth concerning these things; and therefore speak I with openness before him; because not one of these things I think have been hidden from him; for they were not done in secrecy.
Act 26:27 "Believest thou, king Agripos, the Prophets? I know that thou believest."
Act 26:28 King Agripos said to him, (Within) a little thou persuadest me to become a Christian.
Act 26:29 And Paulos said, I would from Aloha that in little and in much, not only thou, but also all who hear me to-day, were as I am, except these bonds.
Witness 2 -- Barnabas is named an apostle in Acts 14:14; he and Saint Paul undertook missionary journeys together and defended Gentile converts against the demands of stricter church leaders (see also Judaizers). They gained many converts in Antioch (AD 43-44), traveled together making more converts (AD 45-47), and participated in the Council of Jerusalem (AD 50). Barnabas and Paul successfully evangelized among the "God-fearing" Gentiles who attended synagogues in various Hellenized cities of Anatolia.
Witness 3 -- Luke the Disciple was the companion of Prophet Paul. He wrote the Book of Acts which he must have investigated and interviewed with the people concerned for accuracy. Prophet Paul is not the author for the Book of Acts.
Prophet Paul said to King Agripos:
Acts 26:27 "Believest thou, king Agripos, the Prophets? I know that thou believest."