Laptop sound cards are, generally speaking, non replaceable - they're often an integral part of the motherboard.
Does the sound fluctuate when using the built in speakers or with external speakers? If it's the latter then it may be the jack plus that's a bit worn and that could be replaceable.
Do you get a "crackle" at any time? If so then it may be a loose connection from the sound card to the internal speakers/output jack which again is fixable.
Its worthwhile updating the drivers, but when its a sporadic fault like this it points to a hardware rather than software issue.
JF