Hi guys! I think i have found the solution for this sound fix. 
Altough it doesn't extract the sound files in the tmp folder except that ExtAudio-0.wav file and when the music of the actual area is fully played, it has nothing to play after, but if you walk further, if you continue to another area, the music plays again with no lagging anymore. I tried at 9am, opened the save files from ch1 to ch5. I'm currently using JPCSP v.3098 for win 64, and there's no sound lagging. If you ask for my settings, i will post it. And thanks for the jpcsp team! (oops, this post is a little longer than i expected 
)
Altough it doesn't extract the sound files in the tmp folder except that ExtAudio-0.wav file and when the music of the actual area is fully played, it has nothing to play after, but if you walk further, if you continue to another area, the music plays again with no lagging anymore. I tried at 9am, opened the save files from ch1 to ch5. I'm currently using JPCSP v.3098 for win 64, and there's no sound lagging. If you ask for my settings, i will post it. And thanks for the jpcsp team! (oops, this post is a little longer than i expected )