It's often the key in the lower left of the keyboard that is labeled Fn (function)

Hold that key down while tapping F8.

A common way to deal with it -
To enable FN Lock on the All in One Media Keyboard, press the FN key, and the Caps Lock key at the same time. To disable FN Lock, press the FN key, and the Caps Lock key at the same time again.

I do not work here, but the benefits are still awesome
Make your sound your own!