Quoting myself here, but I wonder if sound effects from other operating systems released between the early-1980s and early to mid 1990s were used as sources for the sounds in Doom 1 & 2. One could search in the files of Windows 3.0 MME (Multimedia Extensions), Windows 3.1, OS/2 Warp 3, classic MacOS versions 1 through 7 and probably other Unix-based operating systems to find more leads for Doom 1 & 2's sound sources.
Perhaps other early pre-IBM PC home computer sounds were used for Doom 1 & 2's sound sources as well.