That sound is not your spine “cracking” or “popping” like most people think. That 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. In fact, some adjusting techniques use little force and thus produce no noise at all.