I managed to copy the content of my PS2 disc into my computer. However, in comparison to other games that I extracted the audio files, I don't exactly what file I have to try to open, and of course I don't think I'll know how to do it. I've searched a little bit on QuickBMS scripts for psi or pk2 files, but nothing worked.
Here are all the files present in the PS2 disc :
17/03/2005 14:24 7 764 224 bytes # corec.bin
17/03/2005 14:24 930 176 bytes # cored.bin
17/03/2005 18:12 <Folder> ENGINE
14/02/2005 12:28 | 1 229 344 bytes # LegalDut.psi
14/02/2005 12:28 | 1 229 344 bytes # legaleng.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalFre.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalGer.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalIta.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalJap.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalPor.psi
14/02/2005 12:28 | 1 229 344 bytes # LegalSpa.psi
17/03/2005 13:13 68 912 bytes # ps2pak.hsh
17/03/2005 13:12 1 132 271 616 bytes # ps2pak_0.pk2
17/03/2005 13:13 1 021 478 912 bytes # ps2pak_1.pk2
16/12/2004 15:52 64 bytes # FILELIST.DIR
04/11/2003 16:21 266 817 bytes # ioprp271.img
17/03/2005 18:11 <Folder> modules
04/11/2003 16:21 | 24 721 bytes # cdvdstm.irx
15/11/2004 21:49 | 69 261 bytes # cri_adxi.irx
04/11/2003 16:21 | 28 605 bytes # LIBSD.IRX
04/11/2003 16:21 | 95 877 bytes # MCMAN.IRX
04/11/2003 16:21 | 7 417 bytes # MCSERV.IRX
04/11/2003 16:21 | 43 813 bytes # PADMAN.IRX
04/11/2003 16:21 | 8 065 bytes # SDRDRV.IRX
04/11/2003 16:21 | 6 641 bytes # SIO2MAN.IRX
07/03/2005 16:36 | 119 616 bytes # stream.irx
17/03/2005 14:24 720 128 bytes # sles_531.56
14/03/2005 18:00 56 bytes # SYSTEM.CNF
Can you help me ?

If you need or want the files, please let me know.