With a name like "Skyrim Special Edition", you'd expect everything to be better than it was in the original game or, at the very least, as good. Certainly not worse -- if that's even possible. Well, it is for Bethesda, with the PC and Xbox One versions of the game having significantly crappier audio than their PS4 and previous generation counterparts.
After playing the Special Edition for a while and feeling that the "audio seemed... off", a Reddit user by the name "LasurArkinshade" decided to investigate. It's a trivial matter to extract the sound files from the game and analyse them; LasurArkinshade quickly discovered that it wasn't just his imagination.
If you want to listen for yourself, here's an example using the level up sound effect:
Turns out the audio in the Special Edition is heavily compressed. The format used is XWM / XMA, which is essentially Windows Media Audio (WMA). Now, there's nothing wrong with compressing audio, especially for games, as the space savings more than make up for the imperceptible loss in quality. But this is only true if you use a high bitrate, such as 128Kb/s or better.
In the case of the Special Edition, Bethesda seems to have used the default XMA encoding bitrate of 48Kb/s. Which is rather terrible. Here's an audio spectrogram from another Reddit user, withmorten, that shows the difference (original on left, Special Edition on the right).
The downgraded audio is only present in the PC and Xbox One versions of the game, with the PS4 unaffected.
We’re currently testing a fix and hope to have an update out next week.
The downside is I can't see any way of applying a "fix" without getting users to download a fat patch full of uncompressed (or properly compressed) assets. Not such a huge deal in the age of broadband, but still a disappointing effort by the developer.