In poking around the internet I came across to a reference in a book on hypnosis, which suggests you can induce a hypnogogic state by listening to your own breathing: "As a result of listening to the regular rhythm of his own breathing, the subject falls into a hypnagogic state." It says by listening to one's own breath amplified the state is quickly and easily entered. Has anyone tried this? I'm going to give it a try with a USB headset and Audacity.

Hypnotism Comes of Age - Bernard Wolfe, Raymond Rosenthal - Google Books