Those levels are from the WAD Mark created to go along with Brutal Doom, it's called Extermination Day. You can find the download for it in the Forums section of Brutal Doom here on ModDB, under the thread "Bug Reporting (Extermination Day)". There's a pre-beta download there, along with some custom versions (with fixes and unofficial updates) that a few awesome people have been generous enough to share with us. Keep in mind, these aren't the final version. Mark's still workin' on it, far as I know.
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HammerMan2049 - - 2 comments @ Brutal Doom
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HammerMan2049 - - 2 comments @ Brutal Doom
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I found those sounds very annoying too. Yes, there is definitely a way to fix it. I've actually written a tutorial on how to do it here:
You're welcome.
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HammerMan2049
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Just another DoomGuy ripping and tearing through the hordes of demons...