Hi @melissajjjay ,
The TV doesn't provide many audio options and no audio out options at all and reducing the sound level would require modification to the circuit board and the reduced volume would no doubt not be favoured by your father if it is his TV.
Does the TV signal come from an antenna or a box of some description e.g. cable TV box or streaming service device?
If a "box" then I was wondering if it either has an earphone connection or perhaps a Bluetooth option for the audio so that you can connect BT headphones. Getting your father to wear them might be the problem.
If the TV signal comes via an OTA (over the air) antenna you're out of luck unless you buy a new TV that has an audio out or BT function that you can connect headphones to.
If you can get the option to connect headphones somehow, BT or wired, if your father seems unwilling to wear them, suggest that he might appreciate having the sound closer and that he won’t have to struggle to listen as it is direct into the ears with no outside noise getting in the way (if you get the better noise cancelling headphones that is).
Also with BT headphones he can walk around without the danger of tripping over on cable if he wore wired headphones. He could even leave the room and not miss out on what was being said on the TV ;-)