Akai AK2417FHDC User Manual page 23

Select the sound EQ (equalizer) to your desired mode.
EQ Setting
In User mode you can further personalise the sound quality by adjusting EQ frequencies.
AVL (Auto
Turn On to keep the volume level consistent.
Volume Level)
S/PDIF Mode
Set the digital sound output setting.
AD (Audio
Audio Description (AD) provides an additional audio track for visually challenged persons
Description)
(DTV only, subject to program).
Sound Type
Select the desired sound type.
TV SETTING MENUS | 23