Sound disabled randomly

This might just be my computer, but sometimes after a couple games of League I will just lose all sound on my computer. I don't disable sound or mute it, and I'll have sound in champion select, but in game it just disappears. It also disables sound for youtube videos and everything else. I have to restart League to get back sound. I don't mind having to restart, but playing a game without sound can really handicap me because I don't hear pings or other important sounds. Has anyone else had this problem and know of a fix?