try to increase the volume up to maximum, if you can't hear any sound or even humming that means might be the speaker or the audio amplifier itself was the problem. if you have a knowledge in basic trouble shooting you can fix the problem. your first step unscrew and remove the back cover of your unit keep all the screw not to loss. then try to look broken speaker wire and then find the speaker check if their is a resistance.your second step by this time you need trouble shooting if you can use digital tester much better, you need to plug and power ON the TV try to find the amplifier IC sometimes factory used TDA2009. and then you need to check the pin of that particular IC it require supply voltage.if voltage is present then the IC is in normal condition might be the input audio signal was the problem check defective transistor, open resistor or even signal diode going to the amplifier IC.all you need is only concentrate in amplifying section to fix the problem.