This rather depends on the spec of the TV.
Generally speaking plugging in Headphones[wireless or normal] isolated the speaker[s] so that the phone wearer gets the sound and no one else does.
A friend who has a hearing problem discovered a TV set in ASDA[A Schneider] has two headphone sockets.
Plugging phones into one did not isolate the speakers. This meant that he of hard of hearing could set his own volume level whilst those in the room with him could watch with sound set to a normal level.