Did the men with Paul hear the voice or not?

Acts 9:7 and Acts 22:9

1. They heard the voice
   1. (Acts 9:7, NASB) - "And the men who traveled with him stood speechless, hearing the voice, but seeing no one."
   2. (Acts 9:7, NIV) - "The men traveling with Saul stood there speechless; they heard the sound but did not see anyone."
   3. (Acts 9:7, KJV) - "And the men which journeyed with him stood speechless, hearing a voice, but seeing no man"
2. They did not hear the voice
   1. (Acts 22:9, KJV) - "And they that were with me saw indeed the light, and were afraid; but they heard not the voice of him that spake to me."
   2. (Acts 22:9, NASB) - "And those who were with me beheld the light, to be sure, but did not understand the voice of the One who was speaking to me."
   3. (Acts 22:9, NIV) "My companions saw the light, but they did not understand the voice of him who was speaking to me."

This is an interesting difficulty to tackle.  As you can see from the different translations above, at attempt has been made to harmonize the difficulty by translating Acts 22:9 as "did not understand the voice," (NASB & NIV) where the KJV states "... they heard not the voice.."  Literally, the Greek in 22:9 says, "they did not hear the sound."  So, did they or did they not hear the sound?

Various explanations have been offered but the most common is summed up in the following quotes.

"Literally, that clause in 22:9 may be translated, “They did not hear the sound.” The NIV correctly translates the verse, because the verb “to hear” with the genitive case may mean “to hear a sound” and with the accusative case “to hear with understanding.” The genitive case is employed in 9:7, and the accusative is used in 22:9. So the travelers with Saul heard the sound (9:7) but did not understand what Christ said (22:9)."1

Thus in Acts 9:7, “hearing the voice,” the noun “voice” is in the partitive genitive case [i.e., hearing (something) of], whereas in 22:9, “they heard not the voice,” the construction is with the accusative. This removes the idea of any contradiction. The former indicates a hearing of the sound, the latter indicates the meaning or message of the voice (this they did not hear). “The former denotes the sensational perception, the latter (the accusative case) the thing perceived."2

1. 1. Walvoord, John F., and Roy B. Zuck, The Bible Knowledge Commentary, Wheaton, IL: Scripture Press Publications, 1985.
2. 2. Vine, W. E., Vine’s Expository Dictionary of Old and New Testament Words, Grand Rapids, MI: Fleming H. Revell, 1981.