The effects of noise on hearing vary among people. Sudden exposure to loud sounds may psychologically shock people on varying degrees.
Surprise is the emotion we feel when an unexpected event occurs. We need to stop and process the scene in order to decide how to react to the situation. People also come to a standstill when surprised, as they devote all their energy to deciding whether what is unfolding before them is a threat, a joke, a harmless incident.
The human brain takes over and immobilizes us. In doing so, it’s hoped our predator will lose interest and wander off.