The sound is not your spine “cracking” or “popping”. The sound is created by gas (in this case, nitrogen) rushing in to fill the partial vacuum created when the joints are slightly separated. Another example of this phenomenon would be the “pop” sound you hear when the cork is taken out of a champagne bottle. Not all chiropractic adjusting techniques produce this noise. Contrary to popular belief, this noise is not needed for an adjustment to provide relief to the surrounding tissues.