These are the original HL2 sound files, to be used together with Synapse's HL2 pack. This should fix the lipsync issues if this is important for you.
Just replace the original sound folder inside your half-life 2 install directory.
- remove hl2/sound in your HL2 folder
- unpack with 7zip the hl2sounds.7z
- move the new sound folder to hl2/
- play!
Now, the lipsync should work.