PSYC 1000 - Chapter 5d: The Auditory Sense: Hearing

Comprehensive vocabulary flashcards covering the physical properties of sound, auditory anatomy and physiology, pitch perception theories, auditory brain pathways, localization, and forms of hearing impairment.

Hearing (the auditory sense)

Involves less cortical area than vision (but still important), important for detection of objects in environment (e.g., alerting function), important for communication - languages are mostly spoken (and heard). Hearing is most sensitive to sound frequencies corresponding to human vocalization! We also hear sounds over a large range of intensities (e.g, 1 trillion times more energy in sound coming from a jet engine than from a faint whisper).

Sound Waves

Vibrations of the air within the audible frequency range that originate from a vibrating source, characterized by alternating cycles of high and low pressure.

Frequency

The number of cycles per second in a sound wave, measured in Hertz ($\text{Hz}$), which determines the perceived pitch of a sound.

Hertz ($\text{Hz}$)

The standard unit of measurement for wave frequency, where one Hertz represents one cycle per second.

Human Auditory Frequency Range

The spectrum of frequencies detectable by human ears, spanning from $20\,\text{Hz}$ to $20{,}000\,\text{Hz}$, with optimal sensitivity occurring between $200\,\text{Hz}$ and $5000\,\text{Hz}$ (the range corresponding to human vocalization).

Amplitude

The magnitude or vertical height of a sound wave, measured in decibels ($\text{dB}$), which determines perceived loudness (e.g., a faint whisper - 30dB, a loud concert - 120dB).

Decibel ($\text{dB}$)

A logarithmic unit used to quantify sound pressure intensity, where every $10\,\text{dB}$ increase corresponds to a 10-fold increase in physical sound pressure and approximately a doubling of perceived loudness.

Tympanic Membrane

The eardrum; a thin membrane at the end of the auditory canal that vibrates when struck by incoming sound waves and transfers these mechanical vibrations to the middle ear ossicles.

Ossicles

The three smallest bones in the human body—the malleus (hammer), incus (anvil), and stapes (stirrup)—located in the middle ear that mechanically amplify and transmit sound vibrations from the tympanic membrane to the oval window.

Oval Window

A membrane-covered opening separating the middle ear ossicles from the inner ear that vibrates when struck by the stapes, creating fluid waves inside the cochlea.

Cochlea

A coiled, fluid-filled structure in the inner ear where pressure waves cause movement of internal membranes and trigger sensory transduction.

Basilar Membrane

A structure running along the cochlea that deflects in response to fluid motion, supporting hair cells that translate mechanical motion into neural activity.

Hair Cells

Specialized sensory receptor cells situated on the basilar membrane whose stereocilia bend when the membrane moves, opening ion channels ($\text{K}^+$ and $\text{Ca}^{2+}$) to produce depolarization and release excitatory neurotransmitters.

Auditory Nerve

The bundle of afferent nerve fibers that gathers neural signals produced by hair cells throughout the cochlea and conveys them to the brainstem and higher auditory pathways.

Inferior Colliculus (mid-brain)

A midbrain auditory processing center that receives incoming auditory signals along the ascending auditory pathway and projects them to the thalamus.

Thalamus

A structure in the brain that acts as a relay station for sensory information, including auditory signals from the inferior colliculus before it is transmitted to the auditory cortex.

Auditory Cortex (temporal lobe)

The part of the brain responsible for processing auditory information, located in the temporal lobe. It integrates sound signals received from the thalamus, enabling the perception of pitch, volume, and rhythm.

Tonotopic Map

An orderly spatial arrangement of neurons across the primary auditory cortex in the temporal lobe, wherein neighboring neurons are systematically tuned to adjacent sound frequencies.

Place Theory

The theory of pitch perception proposing that different wave frequencies displace specific locations along the basilar membrane—high frequencies displace the narrow, stiff base, whereas low frequencies displace the wide, floppy apex.

Frequency Theory

The pitch perception theory stating that pitch is determined by the collective rate of neural impulses traveling up the auditory nerve; because individual neurons cannot fire faster than $200$ times per second, it primarily accounts for low-frequency sound perception.

Sound Localization

The perceptual process of identifying the spatial origin of a sound, achieved primarily by detecting differences in overall loudness, interaural loudness differences, and interaural arrival time differences.

Conduction Deafness

Hearing loss resulting from mechanical damage or obstruction in the outer or middle ear structures (such as the tympanic membrane or ossicles) that conduct sound to the cochlea; it can often be alleviated with hearing aids.

Nerve Deafness

Sensorineural hearing loss caused by permanent damage to the hair cell receptors in the cochlea or the fibers of the auditory nerve, commonly linked to aging, infection, trauma, prolonged loud noise, or genetic factors.

Cochlear Implant

An electronic medical device that converts sound waves into electrical pulses to directly stimulate the auditory nerve fibers via an electrode array threaded inside the cochlea, restoring functional hearing in cases of nerve deafness.

Cocktail Party Phenomenon

The perceptual capability to attend selectively to a single auditory conversation within a noisy environment while retaining the capacity to notice personally significant stimuli, such as hearing one's own name spoken across a room.