Solved! No sound

Solution
Have you checked that the volume level on the actual youtube mediaplayer/streaming app is not all the way down or muted? It is the speaker icon next to the play/pause button on the bottom left corner of the player. When you place mouse pointer over it a volume slider bar will appear so you can adjust levels. If it is muted a small cross will be displayed next to speaker. Just click speaker to unmute.
Have you checked that the volume level on the actual youtube mediaplayer/streaming app is not all the way down or muted? It is the speaker icon next to the play/pause button on the bottom left corner of the player. When you place mouse pointer over it a volume slider bar will appear so you can adjust levels. If it is muted a small cross will be displayed next to speaker. Just click speaker to unmute.
 
Solution
I very much doubt this is a driver problem tonnyts as patriciaford states all other sounds are fine. And I am sure there are more online experts giving out free advice here than the paid for advice you are advertising.