HP EliteBook 8440p sound failure

Hi! This is probably the most dramatic experience ever while using a computer or a laptop. Two days ago I was using my laptop and as usual performing different activities simultaneously. So at one instance my sound is working fine and I can hear it properly, the next second its gone. I switched to different songs to check it and the result was same. I also noticed that the light of the speaker on top of my keyboard changed to orange automatically which indicates mute or no sound and obviously it wasn't mute and I checked it too. Why did this happen and what is its solution?
