Whether you can use TV speakers and headphones at the same time depends on your TV and how the headphones are connected.
Option 1: Connect to the set-top box
Find the audio output jacks on your cable box, DVR, or set-top box and connect your headphones there. This allows the TV speakers and headphones to operate independently.
Option 2: Use the TV's independent output setting
Check your TV's manual for a setting that allows the TV speakers and audio output jacks to work independently (sometimes called fixed output). Connect your headphones to the TV's audio output for independent operation.
Note: Connecting to the TV's dedicated headphone jack will usually mute the TV speakers – you will only hear audio through the headphones.