From the manual.
Audio sync
With the audio sync function, you can synchronize audio and
video to make sure that no delay is heard from your video content.
1. On the remote control, press and hold for more than three
seconds and then, press +.
2. Within five seconds, press + or - on the remote control to
adjust the audio delay and match with video.
→ The audio sync timing is displayed.
NOTES:
− If no action is taken within five seconds, you will exit the audio sync
mode.