5.3 Hearing

Hearing processes sound waves, which are characterized by frequency (pitch) and amplitude (loudness). High frequency means high pitch (e.g., Mariah Carey), while low frequency means low pitch (e.g., Vin Diesel). Amplitude, measured in decibels, determines how loud or soft a sound is. Excessive exposure to loud noises can lead to hearing loss, particularly of high-pitched sounds first.

The outer ear funnels sound waves to the tympanic membrane (eardrum). The eardrum's vibrations then transmit to three tiny bones in the middle ear: the hammer, anvil, and stirrup. These bones amplify the vibrations and pass them to the cochlea in the inner ear.

Inside the fluid-filled cochlea, vibrations cause hair cells to move. When these hair cells bend, they convert the mechanical vibrations into neural messages. These neural impulses are then sent via the auditory nerve to the temporal lobe of the brain, where they are perceived as sound.

The vestibular system, located in the ear, is crucial for maintaining balance. The semicircular canals within this system contain fluid and motion-sensitive crystals called otoliths. Movements of the head cause these fluids and crystals to shift, sending signals to the brain to adjust balance. Issues like ear infections can disrupt this system, causing dizziness or vertigo.