How can I activate Mac speech without pressing a key? I just bought a microphone to test built in mac speech. On the speech preference, I can choose which keyboard key to make mac to listen to my voice.

Is it possible to make my mac to listen continuously without pressing a key?

I know that I can make mac listen to me without a voice command (ex: mac, [command]), but i don't like it..
This is quoted directly from the Speech Recognition Settings preferences:



Listen only while key is pressed:


  With Speakable Items turned on, you can also select this method by
  speaking the command “Turn on push-to-talk.”


Listen continuously with keyword:


  Use the “Keyword is” pop-up menu to change when you need to speak the
  keyword. Use the Keyword field to specify what the keyword is.