Hearing: Physiology and Psychoacoustics - Flashcards

Flashcards covering key vocabulary terms and definitions from the lecture on Hearing: Physiology and Psychoacoustics, including sound properties, auditory system structures, neural coding, psychoacoustics, and types of hearing loss.

Function of Hearing

Helps you stay aware of your surroundings; Identify & recognize objects in the world based on the sounds they produce.

Sound

Created when objects vibrate, causing molecules in the surrounding medium to vibrate and creating pressure changes.

Amplitude or Intensity

The magnitude of displacement (increase or decrease) of a sound pressure wave, perceived as loudness.

Frequency

For sound, the number of times per second that a pattern of pressure change repeats, perceived as pitch.

Loudness

The psychological aspect of sound related to perceived intensity (amplitude).

Pitch

The psychological aspect of sound related mainly to the perceived frequency, where low frequencies correspond to low pitches and high frequencies to high pitches.

Timbre

The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar.

Decibels (dB)

The unit of measure for the physical intensity of sound (sound pressure level).

Hertz (Hz)

The unit of measure for frequency, where 1 Hz equals 1 cycle per second.

Human Hearing Range

The limited range of frequencies (20-20,000 Hz) and sound pressure levels (dB) that humans can hear.

Sine wave (Pure tone)

The waveform for which variation as a function of time is a sine function, not common in everyday sounds.

Complex sounds

Most sounds in the world, which can be described as a combination of sine waves using Fourier analysis.

Fourier Analysis

A mathematical technique that decomposes a complex function into simpler, constituent sine and cosine waves.

Spectrum (of sound)

A display showing how much energy is present in each of the frequencies in a complex sound.

Harmonic spectrum

The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency.

Fundamental frequency

The lowest-frequency component of a complex periodic sound.

Spectrogram

A pattern for sound analysis that provides a three-dimensional display, plotting time on the horizontal axis, frequency on the vertical axis, and intensity in color or gray scale.

Auditory System (Mammalian)

System composed of the outer, middle, and inner ear, responsible for hearing.

Pinna

The external part of the ear that collects sounds from the environment and funnels them into the ear canal.

Auditory Canal (Ear Canal)

The canal that funnels sound waves from the pinna to the eardrum, enhancing certain sound frequencies; also insulates and protects the tympanic membrane.

Eardrum (Tympanic Membrane)

A membrane that vibrates in response to sound, moving the malleus; it forms the border between the outer and middle ear.

Ossicles

Three small bones (malleus, incus, stapes) in the middle ear that amplify sound waves and transfer their energy to the cochlea.

Malleus

The first ossicle in the middle ear, which receives vibrations from the tympanic membrane.

Incus

The second ossicle in the middle ear, which is vibrated by the malleus.

Stapes

The third ossicle in the middle ear, which transmits vibrations to the oval window.

Oval Window

The membrane at the border between the middle and inner ear, vibrated by the stapes.

Acoustic reflex

The tensing of muscles in the middle ear when sounds are loud, which muffles pressure changes.

Inner Ear

The deepest part of the ear where fine changes in sound pressure are transduced into neural signals.

Cochlea

A spiral structure of the inner ear containing the organ of Corti and filled with watery fluids in three parallel canals.

Vestibular canal (scala vestibuli)

The canal closest to the ossicles, extending from the oval window to the helicotrema, through which pressure waves move first.

Tympanic canal (scala tympani)

The canal extending from the helicotrema at the apex to the round window at the base of the cochlea.

Middle canal (scala media)

The canal sandwiched between the vestibular and tympanic canals, containing the cochlear partition.

Helicotrema

The apex of the cochlea where the vestibular and tympanic canals meet.

Round Window

A membrane at the base of the tympanic canal that releases excess energy from sound waves into the middle ear.

Perilymph

The fluid filling the vestibular and tympanic canals.

Endolymph

The fluid filling the middle canal, showering the cochlear partition in nutrients and ions necessary for hair cell activity.

Stria vascularis

Specialized tissue in the middle canal responsible for balancing charged ions in the endolymph.

Reissner's membrane

A thin sheath of tissue separating the vestibular and middle canals in the cochlea.

Basilar membrane

A plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea.

Organ of Corti

A structure on the basilar membrane of the cochlea composed of hair cells and dendrites of auditory nerve fibers; it translates movements into neural signals.

Hair cells

Cells in the organ of Corti that support stereocilia, which transduce mechanical movement in the cochlea into neural activity sent to the brain stem.

Stereocilia

The tips of hair cells that, when flexed, initiate the release of neurotransmitters.

Tectorial membrane

A gelatinous flap connected at one end that rests on top of hair cells.

Inner hair cells

Hair cells that convey almost all information about sound waves to the brain using afferent fibers.

Outer hair cells

Hair cells that receive information from the brain using efferent fibers and are involved in an elaborate feedback system, making inner hair cell responses more sensitive and sharp.

Place coding

The concept that responses of individual auditory nerve (AN) fibers to different frequencies are related to their place along the basilar membrane of the cochlear partition.

Characteristic frequency (CF)

The frequency to which a particular auditory nerve fiber is most sensitive; its response is clearest when sounds are faint.

Two-tone suppression

A decrease in the response (firing rate) of one auditory nerve fiber to one tone when a second tone is presented at the same time, especially if the second tone is lower in frequency.

Rate saturation

The point at which a nerve fiber is firing as rapidly as possible, and further stimulation is incapable of increasing the firing rate; increasing intensity widens an AN nerve fiber’s frequency selectivity.

Temporal code (for sound frequency)

Information about the particular frequency of an incoming sound wave coded by the timing of neural firing as it relates to the period of the sound.

Phase locking

Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency.

Volley principle

An idea stating that multiple neurons can provide a temporal code for frequency if each neuron fires at a distinct point in the period of a sound wave but does not fire on every period.

Cochlear nucleus

The first brainstem nucleus where afferent auditory nerve fibers synapse.

Superior olive

A brainstem nucleus where inputs from both ears can converge.

Inferior colliculus

A midbrain nucleus in the auditory pathway.

Medial geniculate nucleus

A part of the thalamus that relays auditory signals and receives input from the auditory cortex in the temporal lobe.

Primary auditory cortex (A1)

The first area within the temporal lobes that processes acoustic information.

Belt area

A secondary auditory area where neurons respond to more complex characteristics of sounds, receiving projections from A1.

Parabelt area

An auditory area beyond the belt area, where neurons respond to more complex characteristics of sounds and receive input from other senses.

Tonotopic organization

An anatomical arrangement in which neurons that respond to different frequencies are organized in order of frequency, maintained from the cochlea through primary auditory cortex.

Psychoacoustics

The branch of psychophysics that studies the psychological correlates of the physical dimensions of acoustics to understand how the auditory system operates.

Audibility threshold

The lowest sound pressure level that can be reliably detected at a given frequency.

Equal-loudness curve

A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.

Temporal integration

The process by which a sound at a constant level is perceived as being louder when it is of greater duration, occurring over an interval of 100 to ~200ms.

Masking

Using a second sound, frequently noise, to make the detection of another sound more difficult.

White noise

Noise consisting of all audible frequencies in equal amounts.

Critical bandwidth

The range of frequencies conveyed within a channel in the auditory system, beyond which a sound is no longer perceivable amid noise.

Hearing Loss

The increasing need for higher sound levels to detect and understand a sound, beyond just sensation to perception.

Cochlear implant

Tiny flexible coils with miniature electrode contacts threaded through the round window toward the cochlea apex; signals from a microphone activate electrodes at appropriate positions along the implant to restore hearing.

Conductive hearing loss

Hearing loss caused by problems with the bones of the middle ear.

Otosclerosis

A serious type of conductive hearing loss caused by abnormal growth of middle ear bones, which can be remedied by surgery.

Sensorineural hearing loss

The most common and serious auditory impairment, due to defects in the cochlea or auditory nerve, often from injured hair cells, certain drugs, or metabolic issues.

Damage to hair cells (noise-induced)

Permanent damage caused by excessive exposure to noise, either due to high volume (above ~120dB) or prolonged duration.

Temporary threshold shift

Swelling of hair cells resulting in muffled sounds, which can be temporary unless exposure to loud noise is repeated.

Tinnitus

The sensation of 'ringing in your ears,' caused by extended exposure to loud sounds.

Hidden hearing loss

Damage to hearing from a loss of synapses between auditory nerve fibers and hair cells, resulting in less connectivity for information transfer in the auditory cortex, even if basic sensation is intact while perception is damaged.

Presbycusis

Age-related hearing loss.

Hearing aids

Electronic devices that do more than just amplify sounds; they compress sound intensities into a range the user can hear, rather than amplifying all sounds.