Do two tests:
1) Look in your headphone jack and check to see if there is a red light.
2) Check the sound system preference panel and see if sound is being output to "digital out" instead of "internal speakers."
If the answer to both is yes, then the computer is trying to output to the jack because it thinks there is something there (hence the red light). This is a decently documented problem (both here and on google). The problem tends to recur when you put something in the jack and take it out, but the computer doesn't realize that you've removed the peripheral. The solution either involves sending the thing back to Apple or poking around the headphone jack until you flip the detector and turn the red light off.
Lol I was having this problem today for about half an hour I was troubleshooting it and trying to solve the problem. I saw this thread and it said check for a red light near the headphone place and then guess what...?
hi i have the same problem with my macbook air, except I don't have any red light, the headphone thing didn't work and resetting the PRAM didn't work either. Happened about 2 weeks ago but then it was fine after a week and now once again after about a week it has started doing the exact same thing. I looked at the system preferences and checked my output device but none are showing. There are no output devices available and I cannot seem to install one.
Can anyone help?
I HAD the same problem but I figured out what I did wrong. Before you get all excited, this may not work because my situation was different. I recently downloaded a recording software where it had its own volume thing.. So, it kinda installed into my MacBook and I didn't know, but then I tried controlling my volume but, it was stuck on full blast, couldn't do anything 'bout it. But, what I did was go to System Preferences and clicked on sound, then I clicked output and noticed that it was selected onto the other volume thing, so then I chose the Internal Speakers, which are Built-in and then yeah, it worked again!