Hi @Shobha Tours
What is the source of the signal to the TV, antenna input or input from a "box" e.g. HDMI or Component video etc?
If antenna input have you tried the headphone jack on the back of the TV to hear if audio is available there?
If HDMI etc have you tried a a power refresh of the "box" i.e. turn the power to the "box" off and on and check for audio?
If still no good try another input or input type or even a signal source e.g dvd player to try and isolate the problem further.