well two things come to mind
1st: is your tv capable of the same resolution as your laptop
2nd: Are you connecting via an HDMI cable or VGA?
if HDMI, then audio should be transmitted via the HDMI cable,
if using VGA, then you will need to use an audio cable from the laptop
(headphone jack, 3.5mm) to the TV's audio input jack(s) (RCA). This would be a 3.5mm to dual RCA ended cable