How to reverse: sudo nvram SystemAudioVolume=%80?

Hello,

I recently followed some advice found on a discussion board here to silence the startup chime on my iMac.

This was the terminal command I entered: sudo nvram SystemAudioVolume=%80

Now my Facetime audio output won't work. All other system audio seems fine. How do I reverse this command? I can deal with the startup chime, but I need people to hear me on Facetime.

Thanks for any help in advance.

Steve