26-28 inch 1080P smart flat screen TV with audio output

Many TVs have an optical audio output that works with an adapter. The problem I have found is that, for some reason, they output a loud roar when used with a tv that is receiving an over-the-air signal. This happens with 2 different TVs and 2 different adapters. They work with any other input, like a DirecTV signal or DVD player.

I know these devices have their own a/v outputs. I was just experimenting.