I help the author of Audio Overhaul for Skyrim, LoRd KoRn, with patches and the installer for his mod, and also try to answer tech support help questions in the comments thread.
Recently, a user asked about a very similar problem as you, though it was with his loudspeakers. I believe your problem is related to the same issues as him, so I am re-posting my reply to him here, to help anyone having the sound of NPCs speaking cut out or get too quiet when they move or you turn your player character's camera to a different view:
I suspect your problems with volume level of NPCs voices, etc., are related to Skyrim outputting "true" surround sound to your speakers.
For many people the Skyrim sound engine does not output to discrete multi-channel surround systems correctly, meaning that a "forced" stereo or "virtual surround" option must be enabled to hear a coherent sound environment.
Much of the problem is related to Skyrim's two output models, called Defined Speaker Output (DSO) and HRTF (head-related transfer function). Basically HRTF sounds are directional, while DSO sounds should be heard the same regardless of the direction your character is facing (such as the failed sneak attack sound.)
I'm going to guess that what is happening with your speakers is that they are set up to present discrete surround sound, but for some reason they are only playing the front channels. So when you character is facing away from any NPC
that is talking, you do not hear the rear channel output at all, so it seems that their voice becomes very quiet or silent. Then, when using headphones, most sound drivers will automatically switch to stereo mixdown, or simulated (virtual) surround, which then "fixes" the problem, because you will hear the rear channel output from HRTF sounds mixed into your two headphone speakers.
In fact, if you can get true 4.0 or 5.1 surround output from Skyrim (ie., using 4 or 6 speakers,) it might a lot better mixed because of the front and rear channels all playing any DSO sounds. This is because, due to an error in the way the Skyrim sound engine was designed, when outputting to stereo, DSO sounds have 200% amplitude compared to HRTF because the front and rear channel output are combined. There is a mod which specifically tries to address this stereo output issues, called Stereo-Sounds Volume Fix
, if you want to read a much more technical and detailed explanation of this. However, LoRd KoRn has already made adjustments in AOS
to attempt to address the same issues as Stereo-Sounds Volume Fix, so that mod should not be used with AOS
Bottom line, I would recommend to try changing your speaker sound settings to stereo output and see if that resolves the NPC
voice volume level issue.
Now, I am not sure whether the drivers for your sound hardware have been properly updated for Windows 10, but based on what I said above, you should try turning on Virtual Surround, and leave the sound quality at 24bit 44100Hz - I see numerous reports that changing to higher sample frequency rate such as 48000Hz or 96000Hz causes Skyrim to crash.
You can also read more on this old, but still relevant gamesas.com forum thread.