Q: MacBook Air no audio output device found ???????? *please help*

Yes, unlikely as it semed, this solved this problem on a 2007 (I bought it because they last a long time) imac. I cannot be absolutely certain of the trigger which caused the loss of sound output but the problem certainly arose at about the time I upgraded the operating system to Mountain Lion.  Internal speakers continued to work ok.

I used headphones and for what is worth I plugged and unplugged them a couple of times and then (this seemed to be the important bit) adjusted the volume in the system preferences and the sound returned after what has been several weeks without use of a Bose speaker system.

Thankyou rynelandt.

Joe Holt solution solved my audio problem. Probably when I installed a new battery I moved the audio cable connectors.

Many thanks for your perfect explanation and pictures.

Fixed!

I first tried every solution in this thread, with no success. I reset the PRAM, fixed file permissions (disk utility), rebooted multiple times, plugged in USB-headset, plugged in minijack, and even tried to install the latest combo update (which for some reason fails). The sound device was missing also when i booted into safe mode.

However, I did manage to fix the problem by booting into recovery mode (hold cmd+r while booting), and then simply reinstalling OS X. This doesn't erase or change any user content, so everything will be just as before when the installation is finished. (But as always - do have a backup just in case!) It just reinstalls the system files. And, the sound device problem was fixed. Yay!

Yes!  1000 times yes!  Apple told me I was going to need a new logic board but that sounded like a heap.  If you have the problem with the greyed out volume and no inputs, don't pay Apple a dime until you try the trick in this video.  Just move the audio cable from under the battery to the top of the battery.  Pure effin magic.

Exactly the same to me. No sound, no source. 1st gen MBA, 80 GB.

I tried everything. The SMC. Reinstallation of SL, plugging and unplugging headphones, deleting plist, repair permissions, toying with settings, zap PRAM. Nada. Nothing.

I suspect it's the cable, probably because of overheating placement under the battery, poor design with folding ribbon cable.

Then the hinge broke... Apple is no longer standing behind that problem.

I've stood behind Apple since day one. I have a bushel basket of their products. 

We are all getting rotten Apples!!!!

I had the same problem no sound I tried resetting holding command option and P,R it would work for an hour then be gone again.

Then I tried holding command and D down while I restarted my computer the whole way through the restart and shazam it worked and I still have the sound for a full day now.

Fingers Crossed

This fixed my problem too! Thank you. I just went to System Preferences > Sound, clicked "output," and selected "headphones" (while wearing my headphones.

Headphones in and out and in and out. Do this until you see in system Preferences / Sound that Digital Output changes to Internal Speakers.

Such an old problem, but stil existing in the latest OS X releases.

(And I hate the situation when I really need my internal speakers and there is no headphones around me to be found)

Civix74 was right. I spent 2 hours reinstall OS X last night. After it was done, my mba restarted twice still no speaker. I gave up, went to bed. This morning when I turned on my mba the magical chime came with the boot screen! I turned it off during lunch, and turned it on again. Again the heavenly chime came out from the speaker. It's fixed! Halleluya!

I'm having the same problem, tried the PRAM reset but that just seems to be a temporary fix, so i ended up taking it to the genius bar and getting the logic board replaced. Then a month later to the date, it started happening again. So now i'm at a loss of what to do.

Plug some normal headphones in and out again, repeat until you see the 'Internal Speakers' entry showing up again in 'System Preferences / Output'

There is no other fix available.

I started experiencing the "No audio output device" issue out of the blue about a week ago and had not made any OS upgrades, installed new programs or damaged my MBA in any way. I tried all the other recommendations listed but they all failed after a few moments and I was soundless again. Changing the placement of the audio cable as outlined in this video worked perfectly and I have not had further issues.

I will update if the issue reemerges.

Took my macbook to the apple store a few times with this issue, first had the logic board replaced, then the flex cable, third time i took it for repair they replaced the I/O board. The sound seems to be back now and havent had any issues since.

Re-routing the audio cable fix held for about 3 days, but sadly, my MBA is out of sound once again.

May I know how much did it cost to replace the I/O board? Thanks.