During sleep or deep meditation, our brain undergoes specific changes in neural activity and consciousness, which can affect our perception of external stimuli, including sounds. Here are a few reasons why we may not hear sounds during these states:
Altered Brain Waves: During deep sleep or meditation, the brain exhibits different patterns of electrical activity characterized by slower brain waves. In deep sleep, slow-wave sleep (SWS) dominates, while in meditation, various states can be experienced, including relaxed or focused states with alpha or theta brain waves. These altered brain wave patterns can reduce our responsiveness to external stimuli, making it less likely for us to consciously perceive sounds.
Selective Attention: When we sleep or meditate, our attention tends to be inwardly focused or directed towards internal experiences. This inward attention can lead to a reduced awareness of the external environment, including sounds. The brain filters out sensory inputs that are not deemed important or relevant to the current state of consciousness, allowing us to maintain a state of relaxation or mental concentration.
Thresholds for Sensory Perception: Even when asleep or in deep meditation, our sensory organs continue to receive stimuli. However, the thresholds for sensory perception may be elevated during these states. It means that the intensity of sound required to elicit a conscious perception may be higher compared to when we are awake and actively processing sensory information.
Habituation: Habituation refers to the brain's ability to become accustomed to and ignore repetitive or non-threatening stimuli over time. During sleep or meditation, our brain may habituate to ambient sounds, considering them as non-threatening or irrelevant. As a result, our conscious awareness of those sounds diminishes.
It's important to note that while we may not consciously perceive sounds during sleep or deep meditation, our auditory system is still active and can respond to loud or abrupt noises as a protective mechanism. This is why we can wake up to loud alarms or sudden sounds even when we are in deep sleep.
Overall, the reduced perception of sounds during sleep or meditation is a result of altered brain activity, selective attention, elevated sensory thresholds, and habituation processes that prioritize internal experiences and promote a state of relaxation or focused awareness.