Twisted Metal: Head On sound issues

Okay, I am having major sound issues while playing Twisted Metal: Head On off of my memory stick that were not present while playing off of the UMD. Specifically, only the music in the background plays instead of both the music and sound effects (explosions, machine gun fire, etc.).

Has anyone else encountered this problem? More importantly, does anyone know how to fix this problem?

Obviously, I am using an ISO, however I own the game and created the ISO myself because the load times are better on the memory stick.

The game does work on the UMD and the sound options have the sound effects turned up to max, so they are not disabled.

I think that pretty much covers any stupid mistakes.

Thank you in advance for your help.:)

same here

when I play story mode, most of the sound effecs are missing (including machine gun sounds) only backgroung music and very rare sound effecst are avaiable.

but, if I play other modes, sound effects are ok.

is there a solution ?