Question

Why don't we hear sound while sleeping?

Answer 1

First of all, it totally varies from person to person and the stage of sleep. While you are sleeping, your brain continues to register and process sounds on a basic level. Noise can jostle your slumber—causing you to wake, move, shift between stages of sleep, or experience a change in heart rate and blood pressure—so briefly that you don't remember the next morning. How sounds disturb your sleep depends on factors such as the stage of sleep you're in or the time of night. Noises are more likely to wake you from a light sleep (stages 1 and 2), than from a deep sleep (stages 3 and 4), and tend to be more disruptive in the second half of the night.