The Audio tab is divided into the Preview and Decoding areas. You can define audio quality settings in this tab.      
The Preview area features a drop-down menu. You can use this menu to choose the preview mode for audio that is best suited to your hardware and to your speakers.
The Decoding area features the Apply Dynamic Range Compression when decoding Dolby Digital(TM) tracks check box. If this check box is selected, the level control for Dolby Digital tracks is adjusted in order to reduce hissing and static noise.  
See also
Basic Settings


Audio Tab