I had a similar problem, and apparently others do to. I followed this guide and that fixed it for me. Maybe it will help you aswell.
EDIT: As requested, I will C&P the steps explained in the link below:
- On the control panel > hardware and sound > sound menu
- Select your speakers (realtek high definition audio for me) and
choose > properties > then go to enhancements tab > and check the
loudness equalization box, then re-launch skyrim, and check for
differences on audio.
- This helped me but then I went to the SRS tab on the sound menu
checked to enable SRS technology (this is from realtek HD audio
controller) and selected the game option then the game really sounded
really good and noticed I can hear everythig just fine and not with