Can I ask which Mac you have?
How I wish! I have a G4 Quicksilver and "sleep" is not listed in the commands I can use. With mine I click on Preferences, Speech, Speech Recognition, Open Speech Items Folder. I didn't realize it changed with the Mac being run, but I guess that makes sense, i.e., something newer would have more spoken commands, etc.
Do you have Linux on your system with Mac OS on it too? I want to do this, but I am wondering if it is even possible. I know it is possible with Windows. I want Mac OS, Windows, and Ubuntu on my system with Boot Camp.