Those who have ever tried running Dune 2 from Windows are most likely familiar with this problem that digitized sounds and speech will seemingly randomly disappear and reappear as the game gets progressively unstable.
I have a retro PC with a Pentium III Processor with Windows 98SE and its DOS Prompt (v7.1).
What I noticed is that in Windows I have to restrict the Processor speed to 333MHz or below, otherwise Dune II will do the intro with subtitles instead of speech. When running it from the pure DOS Prompt this issue not there.
I prefer to run the game from windows 98 instead of pure DOS, as in DOS the game needs so much base memory (under 640k) that I am actually forced to use upper memory blocks.
The above is with Dune 1.07 with your patch.
You can download the fix here.
I am not a member of that forum, so I cannot download it.