The body processes vibration on the skin via  receptors or nerve cells.  Some are closer to the surface of the skin, some are deeper in the skin. There are many different  kinds of receptors that detect different stimuli. 

 

Some are fast responsers, others are slower.  Some  only respond for a little while, then shut off until a change is detected or until you consciously focus  your attentin to them ( like your butt cheeks when you sit down).  Some are more senstive than others.

 

Skin receptors are not equally spread out through all parts of the body.  Your finger tips and lips have many more receptors per square inch than your back. This is called receptor density. This is why vibrations from the KAT may feel different when the device is worn on the inner wrist, versus the calf, versus the back of the neck.