Happy synchronicity everyone! While reorganizing my stuff in preparation for a new journey, I uncovered the book in question ("The Five Tibetans" by Christopher Kilham). Here is the portion I was thinking of, in the chapter on Kundalini meditation, pgs. 79-81. The quote's a little long, but I hope you will find it helpful regarding this issue:
"Turn all your attention to the inside of your head and listen closely. Concentrate initially on the right side of the head, near the inner ear. There will be some sort of sound there. You may hear a light ringing, a soft buzzing, or something akin to a faint rumble. Listen as closely as you can to whatever you hear, with absolute attention. ...
"There are many sounds you might hear, including ringing bells, flute-like tones, falling water, buzzing, the sound of the ocean, and sounds like crickets and birds. ...
"With practice you will find yourself merging with the sound so fully that there is no way to differentiate where you end and the sound begins. You will find yourself in a heightened state of awareness. Remember, what this is all about is liberating energy so you can bring acute and well-honed attention to the moment."