Mind if I ask why? Are you trying to change sounds on TPM game? I think there's a key you can press that does that: press TAB during the game and there will be a folder named 'cache' in TPM folder. It has a lot of the sounds in.
The .IMC files are music files, and they did some kind of goofy compression on them and saved them in a different format. I don't know offhand how to change them into .WAV format, but I'll check into it.
IMX2WAV converts IMC files from TPM, XWA, and any other LEC games that use the format to WAV files. SCUMM Revisited should also do the job, and has the added benefit of being compatible with content from older LEC games.