I wonder whose bright idea it was to combine an mp3 inside a Wave file? Seems completely at cross-purposes to me =\
Where did you get that from? PC Version uses IMA ADPCM, PS2 is an altered version of ADPCM (.VB Container) and Xbox uses WMA8. That converting you did at the end and forcing it back to MP3 (but in a WAVE container) pretty much ruins any quality gain purpose you had intended to do really, if people want that PS2 track, would be easier to just grab the PS2 VB file and then convert from that straight to IMA ADPCM.
Fact is as well, the STEAM Digital version of the game pretty much contains the most recent encodes of the radio, still 32Khz IMA ADPCM, but even at least here Chatterbox gets a massive boost from the low quality version it originally came with.