Some my PC games doesn't play the voices, the games I tested are Batman Arkham Asylum and Command & Conquer 3 Uprising, the background music is fine bet the voices doesn't exist.
I had this problem turned out I had Windows set up for 5.1 sound and was using 2.1 speakers which dont have a center speaker for voice output, the games set the sound output through the Windows sound setting try checking it is not on 5.1 speakers.
I had this problem turned out I had Windows set up for 5.1 sound and was using 2.1 speakers which dont have a center speaker for voice output, the games set the sound output through the Windows sound setting try checking it is not on 5.1 speakers.