Turn off mute mac

its a software problem just reboot it 2-3 times that will get the job done

F10 is the mute/unmute button.

because the sound preferences was greyed this means that you have to re install the driver for your sound card.The sound driver is corrupted insert the dirver into your CD room the run the driver for sound card..

Look on you system at the keyboard and you will find a key that toggles the mute if he pressed it. It will toggle between on and off. Normally the mute key or button will look like a megaphone and if it is muted it will have an x over it. Press it to unmute it. Sometimes if it is a key, you might have to press the FN, CTRL or ALT key while you press and hold the key that toggles the mute.

Another way to remove the mute is to Double Click on the megaphone if you see it at the bottom right near the time. This will bring up the volume control and you just remove the check mark from any that is muted.

Also you can click Start/Control Panel look for volume controls that might be muted and remove the check mark on mute.

Also click Start/Programs/Accessories/Entertainment/Volume Control and remove the check mark on muted items.

Unmute your speakers by pressing "F10".

Press the F10 Button

Open System Preferences/Sound/Input. Look at the bottom of that window where it says:
Output Volume. There's a slider, then to the right a Mute button. Make sure that is not checked.

Go to the top of your keyboard. There is a button with a black sideways bell shape icon on it ( a speaker) (the f3 key)...probably four in from the left starting with esc. Toggle that on. It may be on the mute setting now. It should have waves coming out of it when it is unmuted. To the right of that button (two buttons to the right) is the increase volume control button, the (f5) key. Make sure the volume is up! If it is down all the way you will hear nothing and it will be also muted.
I am not sure why if you go into System Preferences (under the Apple icon) and scroll down to Sound and Output, the mute box cannot be unchecked. Perhaps using the function keys to unmute and increase volume on the top of the keyboard will help.

the key combination should be something like fn+f10 to mute and unmute. Let me know the model # of the laptop so i can assist you further if that doesn't work.

Receiving Calls
1. To answer a call, touch or open the slide.
 If the slide is closed, simply slide it up.
 If the slide is closed, press the Voice
Commands key twice, then touch .
 If the slide is open and the touch buttons are
lit, touch .
NOTE If you touch Left Soft Key [Quiet] while the
phone is ringing, the ringing or vibration is muted
for that call.
NOTE If you touch Right Soft Key [Ignore] while the
phone is ringing, the call will end.



Mute Function
The Mute Function prevents the transmission of
your voice to the caller. To quickly activate Mute
touch Left Soft Key [Mute], then to unmute
touch Left Soft Key [Unmute].

NOTE! while doing this you must call someone then while talking with him touch Left Soft Key [Unmute] to Unmute

Hope it help you out ^_^
try download the manual if you loose it
http://www.cellphones.ca/upload/manuals/lg-vx-8500-manual.pdf