I think you are using DVI to HDMI connection
if you do so .. DVI doesnt support audio .. so you'll need to connect the 3.5audio jack in addition to the HDMI cable ..
if your TV support DVI to HDMI you'll see a 3.5 audio input for DVI in your tv
you have to connect your audio card to this audio input to hear sound from TV speakers
I hope that what you were looking for.