Um... there's nothing in Flash Player to control volume or audio outputs.
The player uses existing audio settings, it doesn't modify them.
Go to: Applications/Utilities and open the AudioMIDI Setup utility
Check your Output settings:
ANYTHING other than 44100 or 48000kHz is going to give you troubles.
If you've got no volume control anymore, then it's an OS X problem.
Thanks Mike did what you suggested and it says no device found on the system. Agree it seems to be a OS X problem have been onto apple support but they seem to think its adobe problem so thought I'd see if anyone else has had the same issue. Have reloaded OS X and the speakers come back on then have downloaded flash player twice and have had the same result of the speakers disappearing. So guess it's back to apple again. Thanks
Well, I don't have a MacBook Air, but I have my Minis with Snow Leopard, Lion, Mt. Lion and Mavericks, and Flash Player works in ALL of them, without ever having any audio hardware problems. Some things like Onyx, Filp4Mac, Perian and others can cause problems with the output. I used to use Flip4Mac till it started killing QuickTime's sound and iTunes. Still though, I think there's something in the OS or maybe in the firmware of the Logic Board that's at the heart of this.