How do you unmute your Macbook Pro?

There are a few things to consider if you can't get sound from your mac's speakers. You should have three volume controls that double as function keys. The one farthest right (looks like a speaker) turns it up, the one in the middle turns it down and the one to the left mutes the speakers. Depending on your setup in system preferences the volume controls may require you to press the function (fn button on bottom left of keyboard) in order to activate the volume controls. If your mac is muted and you plug in headphones, the headphones may emit sound. You can then also mute the headphones by pressing the mute button I explained. (The controls work somewhat independently if you're using headphones or the computer speakers). You may want to look in system preferences under the icon "sound" and make sure the mute button isn't checked. Also check the output tab in the sound preferences and make sure the internal speakers are checked. If you ever use an external audio interface there may be a few more things to consider.

Mike

Did you try this? See link below (only, the prefs file might be called "com.apple.systemsoundpref.plist"
http://discussions.apple.com/thread.jspa?messageID=8562882&#8562882

Plug your headphones in and unplug them several times, jiggling the plug a little as you do it. Sometimes the optical audio-out signal (the red light, which is a laser) in the back of the port gets activated when it shouldn't and "sticks" on. Just like the headphone connection, activating the optical audio out mutes the built-in speakers.

Were you ever able to resolve this problem? I have exactly the same problem.

Have you tried what I suggested above?

This didn't work for me.

I deleted the file but the red light still appears when the headphones aren't in the jack.

I am having the exact same problem. Also I would like to add that in System Preferences there is no option for internal speakers.

I know the speakers are good because they sound off during boot up. I have primarily had my laptop hooked up to my TV for the last year or so.

It is good practice Never to stare into a laser!

Yup, that red light is a laser beam,
albeit very low power but still a laser.
The audio is from the MBP tech specs:
"Combined optical digital input/analog line in (minijack)."

Don't every stare into any audio jack, there might be a laser in there.
Especially one that has a red light coming from it.

This is why the i/o ports on some devices have a little plastic insert or cover.
It is to keep the laser light contained, try not to lose it.

I have had a similar problem, twice, with my PowerBook.

On both occasions the speaker icon in the top toolbar disappeared. When I went into System Preferences there were no internal speaker showing. I called AppleCare and we were on the pooint of returning it for repair when they suggested a safe boot. If you aren't familiar with this check out: http://support.apple.com/kb/HT1455

Both times this has fixed the problem for me.

Good luck