Q: How can I get my speaker sound back on my MacBook Pro?

I have a MacBook Pro version 10.7.5.  Processor 2.4 Ghz Intel Core i5.  Memory 4 GB 1333 Mhz DDR3.  Software  Mac OS X Lion 10.7.5 (11G63b).

My external sound (that comes through the factory installed speakers just stopped working. When I attach earbuds, the sound is fine.  The speaker icon is greyed out on the top bar and is stuck on High (it cannot be adjusted.  I have tried to use both bluetooth on and off to no avail.  Can't figure what happened. Can someone advise me?

Thanks,

Maurice