My Mac laptop wasn't playing any sound, and when I tried to turn the volume up or down, a little circle with the line across it graphic came up, like it was telling me "No sound allowed."
So I searched Google for 'mac laptop "no sound"', and the very first hit recommended: "i stuck a head phone plug in the jack and smacked it a couple times and bam it works".
I tried this method and, bing-badda-bing, "it works"!
1) Google is the best tech support desk ever, way better than doing something dumb like calling the manufacturer.
2) Smacking electronic devices: the fix that never grows old!