Question: The volume on my macbook pro has suddenly become greyed out. I haven't installed any updates or made any modifications to the computer, it just suddenly became greyed out after waking the macbook up from sleeping.

I've tried resetting the PRAM, but I don't hear any chime at all when I start up my computer, no matter how long I wait/how many times the computer re-restarts itself.

There also seem to be no internal speakers detected when I go into system preferences. For both input and output the computer detects 0 devices.

Thanks so much in advance for any help!!

Answer: 
Try switching back to your internal speakers with [alt]-clicking on the speaker icon in menubar. Many interfaces don't support volume adjustment and thus the control becomes greyed out.

![enter image description here](https://i.stack.imgur.com/ytgxf.png)
I just blew into the headphone jack - problem solved!