How to convert .sd audio files to .mp3 format.
Converting Sound Designer Audio Files directly to MP3 Audio Files (.sd to .mp3 conversion) is certainly possible and should be quite easy to accomplish. It appears, however, that your options are somewhat limited.
Audio editing and conversion tools, such as Awave Studio or Pro Tools, will allow their users to export SD files in MP3 format.
A set of audio production tools
Audio editting software with huge format support