The nervous system monitors the people it needs most. Not casually. Carefully. Continuously. The people we are most attached to are the people our nervous system watches with the most vigilance — tracking their emotional state, their proximity, their sounds — because historically, those people mattered most to our safety and survival.

The sound itself is almost never the original source of threat. What your nervous system actually learned, somewhere and at some point, is that this type of sound is a signal. A reliable predictor that something overwhelming, unsafe, or uncontrollable was coming.