I just successfully transfered .caf files to my iPhone, carefully renaming them to match the names of files replaced for voicemail, SMS, etc. The sound files work from my Mac desktop. The files also work when started from the SSH opened file of the iPhone. BUT, they are silent when chosen from the phone itself under the 'settings' menu.
Any ideas? I had to restore from a backup so that I could get original sounds back for VM, etc.