You want the necklace to respond to your voice, but not go crazy at every little ambient noise. Some of this adjustment will happen in the code, but the nice thing about this mic breakout is that it has a teensy little adjustment screw. By configuring the code to respond to a medium gain, you'll have wiggle room to adjust on-the-fly for different environments. You'll be able to turn it down for noisy convention halls or up for quiet storytelling sessions.
Take your teeny weeny screwdriver and twist the gain adjustment screw until it's roughly in the middle of its turning radius.
Now, make some noise. See how loud you need to be for your LEDs to respond.
Look at the code and find the value for NOISE. To make the mic more sensitive, make this number smaller. To make it less sensitive, make this number bigger.