Adjusting AV Synchronization
Sound AV Sync. Adjust and then click On.

TV Speaker | Adjusts the synchronization of the sound from built-in TV speakers. The closer to the minus sign (-), the longer the audio output time. The closer to the plus sign (+), the faster the audio output speed compared to the default.
External Speaker | Adjusts how the sound is synced from external speakers, such as speakers connected to the digital audio output port or LG audio devices. The closer to the minus sign (-), the longer the audio output time. The closer to the plus sign (+), the faster the audio output speed compared to the default. LG audio devices are supported only by models with an optical digital or HDMI (ARC) port.
Bypass | Outputs the broadcast signals or the sound from external devices without any audio delay. The audio may be output before the video because of the time the TV takes to process the video input.