I don't think .int files are audio files, I think they are a type of graphics file but I'm not 100% sure. I think the audio files in this game are .dsp files, if on Gamecube and .str if on PS2, going by known file formats for the systems. I have heard VGSC works on opening these files, but for some reason, it's not working for me, but I only tested the Gamecube version, so I don't know about the PS2 version. Sorry about not having any direct answers, but this is all the information I have right now, and I haven't found any other clues to solve this mystery. 