you should also install atrac3plus2wav. sonicstage will only decode stereo sound files, while the other tool will decode mono ones, which should decode pretty much all at3+ format sounds. most of the voice samples are in mono format to save space, so this will be used often.
http://www.emunewz.net/forum/showthread.php?tid=14984
search for "JPCSP and sound" for instructions.
http://www.emunewz.net/forum/showthread.php?tid=14984
search for "JPCSP and sound" for instructions.