Auditory System: Sound Waves, Ear Anatomy, and Auditory Processing

Vocabulary flashcards covering sound wave characteristics, external, middle, and inner ear anatomy, sensory transduction, theories of pitch processing, loudness safety, and sound localization.

Wave frequency

The number of up and down cycles that occur within one second, typically measured in hertz, which corresponds to the pitch or tone of a sound.

Wave amplitude

The height and depth of sound waves, which corresponds to the wave's energy and affects the perceived loudness or intensity of a sound.

Pinna

Also known as the auricle; the visible outer portion of the ear projecting from the side of the head that gathers and funnels sound waves into the ear.

External auditory meatus

Also known as the ear canal; a slightly S-shaped tube within the temporal bone extending from the outer ear to the tympanic membrane that funnels sound waves to the eardrum.

Temporal bone

A paired, bilateral bone located at the sides and base of the skull (one of eight skull bones) that encases and protects the middle and inner ear.

Tympanic membrane

Also known as the eardrum; a thin, cone-shaped membrane separating the external ear from the middle ear that vibrates back and forth in response to sound wave pressure differences.

Ossicles

A set of three tiny bones located in the middle ear—the malleus (hammer), incus (anvil), and stapes (stirrup)—responsible for transmitting sound vibrations to stimulate the oval window.

Malleus

The outermost bone of the ossicular chain in the middle ear that transmits sound vibrations from the tympanic membrane to the inner ear.

Incus

The small middle bone among the three ossicles in the middle ear that transmits sound vibrations from the eardrum to the inner ear.

Stapes

The smallest and innermost of the three ossicles in the middle ear; a stirrup-shaped bone that transmits sound vibrations from the incus to the inner ear.

Oval window

A small, membrane-covered opening in the bony wall separating the middle ear from the inner ear that leads into the vestibule and is stimulated by the ossicles.

Round window

One of two openings leading from the middle ear into the inner ear, sealed by the secondary tympanic membrane.

Cochlea

A spiral-shaped, coiled bony tube in the inner ear containing fluid, a basilar membrane, and hair cells that performs auditory transduction.

Auditory transduction

The process occurring in the cochlea where the vibration of hair cells triggers neural impulses that transmit sound information to the brain.

Semicircular canals

Three small, interconnected, fluid-filled structures in the inner ear belonging to the vestibular system that help provide spatial orientation and balance information to the brain.

Vestibule

A central chamber within the inner ear that plays a key role in maintaining balance and sensing head movements.

Vestibular nerve

One of the two branches of the vestibulocochlear nerve that transmits sensory information from the vestibular system of the inner ear to the brain.

Place theory

A theory developed in $1857$ proposing that pitch perception depends on the location of stimulation along the basilar membrane, with high pitches activating the beginning and low pitches activating areas further down.

Frequency theory

A pitch theory proposing that the pitch of a sound determines the rate or frequency of neural signals sent along the auditory nerve to the brain within a given interval.

Decibels

The unit used to measure sound volume (e.g., normal conversation measures about $60\,\text{dB}$, while a loud rock concert registers around $120\,\text{dB}$).

Sound localization

The perceptual ability to determine the physical origin of a sound, made possible because the two ears are spaced apart and receive subtle differences in sound timing and intensity.