Yawning, an involuntary act involving deep inhalation and a wide opening of the mouth, often causes a temporary change in hearing. This common experience results from three simultaneous physiological processes within the ear. Auditory perception changes, ranging from immediate muffling of external noise to a noticeable “pop” and the appearance of internal body sounds. Understanding the muscular and pressure mechanics involved explains why the world sounds different during a yawn.
The Temporary Muffling of External Sound
The immediate reduction in outside noise during a yawn results directly from muscle contraction within the middle ear. Two small muscles, the tensor tympani and the stapedius, are automatically activated as part of the muscular effort of a deep yawn. This action is part of the acoustic reflex, which is associated with movements of the jaw and face.
The tensor tympani muscle attaches to the malleus, one of the three tiny bones (ossicles) in the middle ear. When it contracts, it pulls the malleus inward, tensing the eardrum (tympanic membrane). The stapedius muscle contracts and pulls the stapes bone, limiting its movement. This tensing and stiffening of the ossicular chain significantly reduces the transmission of sound vibrations to the inner ear. This effect is perceived as a sudden muffling of external sounds. The muscle contraction also acts as a protective mechanism, partially dampening the intense sounds generated by the jaw movements of the yawn itself.
How Yawning Equalizes Middle Ear Pressure
Following the initial muffling, many people experience a distinct “popping” sensation, signaling the equalization of pressure within the middle ear. This process is managed by the Eustachian tube, a narrow passageway connecting the middle ear cavity to the upper throat (nasopharynx). Normally, this tube is closed.
Yawning triggers the contraction of the tensor veli palatini muscle, which is attached to the Eustachian tube. This action pulls the walls of the tube apart, forcing it to open briefly. The opening allows air pressure in the middle ear to balance with the surrounding atmosphere. When pressure equalizes, the eardrum can vibrate freely again, which is necessary for optimal hearing. This pressure balance is why yawning is often a remedy for ear discomfort during changes in altitude, such as on an airplane.
The Perception of Internal Body Noises
When the external world becomes muffled by the tensing of the middle ear muscles, internal body noises become apparent. The contraction of the tensor tympani muscle, which reduces sensitivity to outside sound, also generates its own low-frequency sound. This muscular vibration is often described as a low rumble, roar, or thrumming sensation heard within the head.
The suppression of external noise allows sounds normally masked by the environment to become audible. These include blood flowing through the carotid artery, the crackling of joints and tissues around the jaw, and subtle muscle contractions in the head and neck. The temporary reduction of external auditory input, combined with muscle tension, makes the body’s own mechanical sounds the dominant auditory experience. This shift resolves as the middle ear muscles relax and the Eustachian tube closes again.