A.T. Robertson Commentary Acts 22:9

"And they that were with me beheld indeed the light, but they heard not the voice of him that spake to me." — Acts 22:9 (ASV)

But they heard not the voice (την δε φωνην ουκ ηκουσαν). The accusative here may be used rather than the genitive as in verse 7 to indicate that those with Paul did not understand what they heard (9:7) just as they beheld the light (22:9), but did not see Jesus (9:7). The difference in cases allows this distinction, though it is not always observed as just noticed about 22:14; 26:14. The verb ακουω is used in the sense of understand (1 Corinthians 14:2). It is one of the evidences of the genuineness of this report of Paul's speech that Luke did not try to smooth out apparent discrepancies in details between the words of Paul and his own record already in ch. 9. The Textus Receptus adds in this verse: "And they became afraid" (κα εμφοβο εγενοντο). Clearly not genuine.