Glossary
Amplitude
The height of a sound wave, which determines the perceived loudness of a sound.
Example:
A rock concert typically features music with a very high amplitude, making it feel incredibly loud.
Anvil (Incus)
The second of the three tiny bones in the middle ear, which transmits vibrations from the hammer to the stirrup.
Example:
Vibrations pass from the anvil to the stirrup, continuing the sound's journey through the ear.
Audition
The sense of hearing, which involves the brain's interpretation of sound waves as meaningful information.
Example:
When you listen to your favorite song, your brain is engaging in the process of audition to interpret the melodies and lyrics.
Auditory Cortex
The region of the temporal lobe responsible for processing and interpreting auditory information.
Example:
When you recognize a familiar voice, your auditory cortex is actively interpreting the complex sound patterns.
Auditory Nerve
A bundle of nerve fibers that carries neural impulses from the cochlea to the brain, specifically to the thalamus and then the auditory cortex.
Example:
Damage to the auditory nerve can prevent sound signals from reaching the brain, resulting in sensorineural hearing loss.
Basilar Membrane
A membrane within the cochlea that vibrates in response to sound waves, supporting the hair cells.
Example:
Different sections of the basilar membrane vibrate maximally to different sound frequencies, a key aspect of place theory.
Cochlea
A snail-shaped, fluid-filled structure in the inner ear where sound vibrations are transduced into neural impulses.
Example:
The cochlea is often called the 'hearing organ' because it's where mechanical sound energy is converted into electrical signals.
Cochlear Implants
Electronic devices surgically implanted to help individuals with sensorineural hearing loss by directly stimulating the auditory nerve.
Example:
For some people with severe nerve deafness, cochlear implants can restore a sense of hearing by bypassing damaged hair cells.
Conduction Hearing Loss
Hearing loss caused by damage to the outer or middle ear that prevents sound waves from reaching the cochlea.
Example:
An ear infection causing fluid buildup in the middle ear can result in temporary conduction hearing loss.
Decibels (dB)
A logarithmic unit used to measure the intensity or loudness of a sound.
Example:
Exposure to sounds above 85 decibels for extended periods can cause hearing damage.
Ear Canal
A passage leading from the outer ear to the eardrum, through which sound waves travel.
Example:
Sound waves travel down the ear canal before reaching the eardrum.
Eardrum (Tympanic Membrane)
A thin membrane located at the end of the ear canal that vibrates when struck by sound waves.
Example:
Loud noises can cause the eardrum to vibrate intensely, sometimes leading to discomfort.
Frequency
The number of complete wavelengths that pass a point in one second, determining the pitch of a sound.
Example:
A high-pitched whistle has a much higher frequency than the low rumble of thunder.
Frequency Theory (Temporal Theory)
A theory of pitch perception stating that the rate of neural impulses traveling up the auditory nerve matches the frequency of a low-pitched tone.
Example:
When listening to a deep bass note, frequency theory suggests that neurons fire at a rate corresponding to that low pitch.
Hair Cells
Sensory receptors located on the basilar membrane within the cochlea that transduce mechanical energy from sound waves into neural impulses.
Example:
When the hair cells bend due to fluid movement in the cochlea, they trigger nerve impulses sent to the brain.
Hammer (Malleus)
The first of the three tiny bones in the middle ear, which receives vibrations from the eardrum.
Example:
The hammer bone is crucial for transferring sound vibrations from the eardrum to the anvil.
Head Tilting (Sound Localization Strategy)
A strategy used to improve sound localization, especially for sounds directly in front, behind, above, or below, by creating differences in sound intensity between the ears.
Example:
If you're trying to locate a faint buzzing sound directly above you, you might use head tilting to create a clearer difference in sound perception between your ears.
Inner Ear
The innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs, responsible for both hearing and balance.
Example:
Damage to the inner ear can lead to significant hearing loss or problems with equilibrium.
Intensity (Sound Localization Cue)
A cue for sound localization based on the slight difference in loudness of a sound as it reaches each ear, with the ear closer to the source perceiving it as louder.
Example:
The ear closer to a whispering person will perceive the sound with slightly greater intensity, helping you locate them.
Loudness
The psychological experience of sound intensity, primarily determined by the amplitude of a sound wave.
Example:
Turning up the volume on your headphones increases the loudness of the music.
Middle Ear
The air-filled cavity behind the eardrum containing three tiny bones (hammer, anvil, stirrup) that amplify and transmit vibrations to the inner ear.
Example:
Infections in the middle ear can cause fluid buildup, impairing hearing.
Outer Ear (Pinna)
The visible, external part of the ear that funnels sound waves into the ear canal.
Example:
The unique shape of your pinna helps collect sound waves from the environment.
Pitch
The psychological experience of how high or low a sound is, primarily determined by the frequency of a sound wave.
Example:
Singing a soprano part requires hitting notes with a very high pitch.
Place Theory
A theory of pitch perception stating that different high-pitched sounds cause maximal vibrations at different locations along the basilar membrane.
Example:
According to place theory, a very high-pitched violin note would cause vibrations primarily near the base of the cochlea.
Sensorineural Hearing Loss (Nerve Deafness)
Hearing loss caused by damage to the cochlea's hair cells or the auditory nerve, often irreversible.
Example:
Prolonged exposure to very loud music can lead to sensorineural hearing loss due to damage to the delicate hair cells.
Sound Localization
The ability to determine the source or direction of a sound, primarily by using differences in timing and intensity between the two ears.
Example:
When you hear a car horn, your brain uses sound localization to pinpoint where the car is coming from.
Stirrup (Stapes)
The third and smallest of the three tiny bones in the middle ear, which transmits vibrations to the oval window of the cochlea.
Example:
The stirrup bone's movement against the cochlea's oval window creates fluid waves in the inner ear.
Thalamus
A brain structure that acts as a sensory relay station, directing most sensory information (including auditory) to the appropriate cortical areas.
Example:
Before reaching the auditory cortex, sound information is first processed and relayed by the thalamus.
Timbre
The unique quality of a sound that allows us to distinguish between different instruments or voices, even when they produce the same pitch and loudness.
Example:
Even if a flute and a clarinet play the same note at the same volume, their distinct timbre allows you to tell them apart.
Timing (Sound Localization Cue)
A cue for sound localization based on the slight difference in when a sound wave reaches each ear, with the ear closer to the source receiving it first.
Example:
If a dog barks to your left, the sound will reach your left ear a fraction of a second before your right, providing a timing cue for its location.
Transduction
The process by which sensory receptors convert physical energy (like sound waves) into neural impulses that the brain can understand.
Example:
In the ear, transduction occurs in the cochlea when hair cells convert fluid vibrations into electrical signals.
Volley Principle
An extension of frequency theory explaining how we hear mid-range pitches, where groups of neurons fire in rapid succession, creating a combined frequency matching the sound.
Example:
For a mid-range sound like a human voice, the volley principle allows neurons to collectively signal frequencies higher than any single neuron could fire.