I don't depend on the sound made by the racking of my shotgun to do my work for me, but ... Aippi is absolutely correct. If you have never heard the sound of a pump shotgun racked in the dead of night while approaching an "unknown condition", you have not heard it all. It can be LOUD and paralyzing to many.
Respectfully and Semper Fi,
Independent Security Contractor, NRA Certified Firearms Instructor, NRA Life Member, and Unarmed Combat Instructor