This can also be done with a program from windows XP.
As it is considered illegal to download a file system, it is better to look for it. It is from windows XP, but that doesn't matter.
If you can find it, here are instructions;
Once you open it, it may say something like, "There was an error updating the registry". That doesn't matter. What you do now, is go to "File", look for "Open..."
Browse to your sound file. When you found your .wav file (Sound effect), choose "Open".
Then, once you opened your file, go to "Properties" from the "File" menu.
Somewhere there may be a "Convert Now..." button. Click that, and on the drop down menu "Attributes", look for "48.000 kHz, 8-bit, Mono". Choose that, and then click ok. Click ok again and close.
Load the file in whatever editor you're using (ex. XWE, Slumped, etc.) and then convert to doom wave.