"... the answer is that the air in the vocal tract acts like the air in an organ pipe, or in a bottle. When you give it a tap it will vibrate. If you open your mouth and make a glottal stop, and flick a finger against your neck just to the side and below your jaw, you will hear a note, just as you would if you tapped a bottle. If you tilt your head slightly backward so that the skin of the neck is stretched while you tap, you may be able to hear this sound somewhat better"
Just try it. I never knew it was possible. But seriously its amazing. You make a glottal stop by producing the word uh-oh. and its the "-" in between. And then just flick your neck under your chin. If you move your tongue around to make the different vowel sounds it changes the pitch slightly.
I've been doing it for like 5 minutes now. I probably have a huge red mark on my neck. Totally worth it.