The first web site is the main site of William Buhlman, an author on the subject of astral projection. Clicking on "OBE Techniques" leads to a link to "Recognition and Response to the Vibrational State", which has this copied text (below) and more. All of these count as the correct vibrational stage.
http://www.out-of-body.com/
http://www.mach1audio.com/out-of-body/techniques/vibestate.htm
Common Vibrational Signals
• Buzzing, humming or roaring sounds
• Unusual tingling or energy sensations
• Voices, laughter, or your name being called out
• Heaviness or sinking
• Numbness or paralysis in any part of your body
• Weightlessness or spreading lightness
• Any internal vibrations out of norm
• Electrical-like sense of energy
• Footsteps or other sounds of a person's presence
• Internal rocking, spinning, or movement of any kind
• Arms or legs lifting while asleep
• Surge of energy flowing through your body
• Any noise out of the norm, wind
I have never experienced vibrations. I am relatively new to the study of bioenergy/chakras/auras and astral projection. I have been into lucid dreaming for a few years now though and so the phenomenon is not new to me in the theoretical sense. Practically, however, I have no knowledge of it.
I will explain the experience I had last night and you let me know if it resonates with your experiences of vibrations. I was exhausted. I have been busy between work and school and trying to make time for my girlfriend. Anyway... I was sitting on the couch last night and began falling asleep while watching tv. Well I suddenly heard this loud buzzing which I though was my cell phone on vibrate. It sounded to be coming from behind me. I got up and went to look for it but it wasn't on the table behind the couch. In fact, there was nothing that I could find in the room that would make that buzzing sort of vibrating noise. SO what was that? I didn't feel vibrations or anything... just the noise.