LG 27UK670 Owner's Manual page 24

No sound from the headphone port or speaker.
are images displayed using DisplayPort or HDMI input
without sound?
NoTE
•
LED can be lighted with set OsD Menu.
settings – General – Power LED – On
24
•
Try increasing the volume using the button on the monitor.
•
set the audio output of the PC to the monitor you are using. On Microsoft windows, go to Control Panel > Hardware and sound > sound > set the monitor as default
device.