If replacing files doesn't solve synchronization issues (where audio doesn't match mouth movements), consider these official community fixes:
If your game installation is incomplete (often seen in "highly compressed" versions or specific repacks), you may need to manually re-add these files or apply community patches. FusionFix (Recommended): gta 4 cutscene audio files download install
Paste them into your own directory (after backing up your originals). gta 4 cutscene audio files download install