Snoring presents a curious paradox: it is a loud, disruptive noise to anyone nearby, yet the person producing the sound remains entirely oblivious. This common nocturnal event is generated by the sleeper’s own body but is effectively silenced before reaching conscious awareness. Understanding this mystery requires examining the physical creation of the noise, the unique way sound travels through the body, and the brain’s specialized filtering mechanisms during sleep. These physiological and neurological processes explain why a snorer can rattle the walls without waking themselves.
The Physics of Snoring: How the Noise is Created
The sound of snoring originates from the vibration of soft tissues in the upper airway during relaxed sleep. As the body enters deeper rest, the muscles of the throat, tongue, and soft palate relax, causing the airway to narrow. This partial obstruction means that air rushing past the area must accelerate, creating turbulent airflow.
This turbulence causes the soft palate—the fleshy, back part of the roof of the mouth—and the dangling uvula to flutter rapidly. The resulting sound is the noisy byproduct of these tissues vibrating against the passing air. The volume and intensity of the snore are directly related to the degree of airway narrowing and the force of the air being inhaled or exhaled.
Differential Hearing: Air Conduction Versus Bone Conduction
The primary reason a snorer does not hear the sound as others do lies in the two distinct pathways sound uses to reach the inner ear. When a sleeping partner hears the snore, the sound waves travel through the air, enter their ear canal, vibrate the eardrum, and pass through the middle ear bones to the cochlea—a process called air conduction. This external path delivers a clear, amplified, and often high-decibel acoustic signal.
For the snorer, the sound travels predominantly through a different route known as bone conduction. The actual vibrations created by the soft palate are transmitted directly through the surrounding solid structures of the head, bypassing the ear canal and eardrum entirely. This internal vibration reaches the cochlea almost instantaneously from the source.
The characteristics of sound traveling through bone are significantly different from those traveling through air. Bone conduction typically transmits lower frequencies more efficiently, causing the internal sound to be muffled, distorted, and lower in fidelity compared to the external noise. The sound level reaching the inner ear via bone conduction is substantially attenuated, or reduced, making it less likely to register as a loud, external disturbance.
Sensory Suppression: Why the Sleeping Brain Filters Out Internal Noise
Even the muffled, bone-conducted sound of snoring is actively filtered out by the brain through a process called sensory gating. Sleep is a state of partial sensory disconnection, where the brain raises its internal “arousal threshold” to protect the continuity of rest. This neurological mechanism dampens the flow of sensory information, making the sleeper less responsive to both external and internal stimuli.
The brain also employs a process of habituation, learning to recognize and ignore repetitive, non-threatening stimuli. Since the internal snoring vibration is constant and generated by the self, the brain quickly learns that this sound does not signal danger, classifying it as background noise. This filtering is particularly effective during deep non-rapid eye movement (NREM) sleep, which has the highest acoustic arousal threshold.
The continuous, low-level internal vibration is dismissed at a subconscious level, allowing the sleeper to maintain their state of rest. Only a sudden, sharp change in the snoring pattern or an extremely loud external sound that overcomes the high arousal threshold would be potent enough to cause a brief arousal.