TServo2049 said:

It really confuses me when older movies have alterations in their mono tracks. It happened with The Wizard of Oz, it happened with Frankenstein, it happened with Dracula. I think it's because due to the age of these films, the mono tracks are now restorations/reassemblies, not just direct transfers of an original mono element.

Yeah it is very strange. For example the 2004 DVD of Dracula strangely uses the censored audio track that removes Renfield's death scream and Dracula's death groans yet the 1999 and 2006 DVDs and the Blu Ray use the uncensored audio. What was going through Universal's mind in 2004 is a mystery. I also wasn't fond how when E.T. was released on DVD that some of the new sound effects added to the 2002 reissue was added to the DVD of the original. An example would be when they police are running to the evacuated van and you hear walkie talkie static.