LOL. because you only have the video connected to the TV. if you want, you can unplug your computer speakers and get the right adapter and then runs those to your TV too.
you will have to get whatever adapter that works with whatever you want it to work on. i assume your tv has inputs for audio? then simply get an adapter that has a mini plug that plugs into the back of your comp and on the other end, has rca jacks that will plug into your TV's inputs.