I sometimes wear headphones while watching TV, so I can have it loud enough without disturbing others. However, if others are present and have the regular sound is on, it won't be quite synched up with the headphones. The result is an echo effect that makes it unbearable.

that plug into the tv, as into any other device.
so they don't make it louder, just means that you can hear it as loud as you want without others hearing it?

you can get an amplifier, either on its own or with a radio, that has an "auxiliary" input. You input your tv to - it assuming your tv has an output (look on the back). Then whenever you want, you turn on the amplifier and its volume is added to the tv volume. You can add a headphone set to the amplifier or listen through speakers. It's what we used to call a stereo setup, but you don't need the phonograph! You can get everything you need on ebay or craig's list, or radio shack.