I also notice the voice isn't there in the game like the theme song in title menu and also when they are in battle, they don't shout out their moves.  I have the 031.48 and follow the guide posted by evilgouki and after created iso, I changed it to psp format and played on psp. 

The game runs fine but there isn't voice. The background music plays fine tho.  I notice someone posted this problem earlier in the thread.  Anyone else have the voice and opening theme song working?

what did you use to make the psp eboot? Every time I make one it says it's corrupt even though it works fine on my comp. (Also I use psx2psp and i've made tons of eboots with it...)

I also use psx2psp, not sure what version that is tho.