Chapter 9 Flashcards
amplitude / intensity
The magnitude of displacement (increase or decrease) of a pressure wave; loudness.
frequency
The number of times per second that a pattern of pressure change repeats; pitch.
hertz (Hz)
A un it of measure for frequency; 1 Hz = 1 cycle per second.
loudness
The psychological aspect of sound related to perceived intensity.
pitch
The psychological aspect of sound related mainly to the fundamental frequency.
decibel (dB)
A unit of measure for the physical intensity of sound. dB = 20 log (p/p0)
sine wave / pure tone
The waveform for which variation as a function of time is a sine function.
spectrum
A representation of the relative energy (intensity) present at each frequency.
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.
timbre
The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar. Timbre quality is conveyed by harmonics and other high frequencies.
pinna
The outer, funnel-like part of the ear.
ear canal
The canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane.
tympanic membrane
The eardrum; a thin sheet of skin at the end of the outer ear canal; vibrates in response to sound.
outer ear
Pinna and ear canal.
middle ear
An air-filled chamber containing the middle bones / ossicles; conveys and amplifies vibration from the tympanic membrane to the oval window.
ossicle
Any of three tiny bones of the middle ear: malleus, incus, and stapes.
malleus
The most exterior of the ossicles; receives vibration from the tympanic membrane and is attached to the incus.
incus
The middle of the ossicles; connecting malleus and stapes.
stapes
The most interior of the ossicles; connected to the incus; presses against the oval window of the cochlea on the other end.
oval window
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside.
inner ear
Hollow cavity in the temporal bone of the skull, and the structure within this cavity: the cochlea and the semicircular canals of the vestibular system.
tensor tympani
The muscle attached to the malleus; tensing it decreases vibration.
stapedius
The muscle attached to the stapes; tensing it decreases vibration.
acoustic reflex
A reflex that protects the ear from intense sounds, via contraction of the stampedius and tense tympani muscles.
cochlea
A spiral structure of the inner ear containing the organ of Corti.
tympanic canal
One of three fluid-filled passages in cochlea; extends from the round window at the base of the cochlea to the helicotrema at the apex; scala tympani.
vestibular canal
One of three fluid-filled passages in cochlea; extends from the oval window at the base of the cochlea to the helicotrema at the apex; scala vestibuli.
middle canal
One of three fluid-filled passages in cochlea; is sandwiched between tympanic and vestibular canals and contains the cochlear partition; scala media.
helicotrema
The opening that connects the tympanic and vestibular canals at the apex of the cochlea.
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.
cochlear partition
The combined basilar membrane, tectorial membrane, and organ of Corti, which are together responsible for the transduction of sound waves into neural signals.
round window
A soft area of tissue at the base of tympanic canal that releases excess pressure remaining from extremely intense sounds.
organ of Corti
A structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers.
hair cell
Any cell that has stereocilia for transducing mechanical movement in the inner ear into neural activity sent to the brain. Some hair cells also receive inputs from the brain.
auditory nerve
A collection of neurons that convey information from hair cells in the cochlea to the brain stem (afferent neurons) and from the brain stem to the hair cells (efferent neurons).
steriocilium
Any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitters.
tectorial membrane
A gelatinous structure, attached on one end, that extends into the middle canal of the cochlea, floating above inner hair cells and touching outer hair cells.
tip link
A tiny filament that stretches from the tip of a stereocilium to the side of its neighbor.
place code
Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency of an incoming sound wave is coded by the place along the cochlear partition that has the greatest mechanical displacement.
afferent fiber
A neuron that carries sensory information to the central nervous system.
efferent fiber
A neuron that carries information from the central nervous system to the periphery.
threshold tuning curve
A graph plotting the thresholds of a neuron in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response.
characteristic frequency (CF)
The frequency to which a particular auditory nerve fiber is most sensitive.
two-tone suppression
A decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.
isointensity curve
A map plotting the firing rate of an auditory nerve fiber against varying frequencies at varying intensities.
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.
rate-intensity function
A graph plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities.
low-spontaneous fiber
An auditory nerve fiber that has a low rate (< 10 spikes/sec) of spontaneous firing; require intense sound.
high-spontaneous fiber
An auditory nerve fiber that has a high rate (> 30 spikes/sec) of spontaneous firing; increase firing rate in response to relatively low levels of sound.
mid-spontaneous fiber
An auditory nerve fiber that has a medium rate (10 - 30 spikes/sec) of spontaneous firing.
phase locking
Firing of a single neuron at one distinct point in the period of a sound wave at a given frequency.
temporal code
Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency of an incoming sound wave is coded by the timing of neural firing as it relates to the period of the sound.
volley principle
The idea 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 brain stem nucleus at which afferent auditory nerve fibers synapse.
superior olive
An early brain stem region in the auditory pathway where inputs from ears converge.
inferior colliculus
A midbrain nucleus in the auditory pathway.
medial geniculate nucleus
The part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex.
tonotopic organization
An arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency.
primary auditory cortex (A1)
The first area within the temporal lobes of the brain responsible for processing acoustic information.
belt area
A region of cortex, directly adjacent to the primary auditory cortex (A1), with inputs from A1, where neurons respond to more complex characteristics of sounds.
parabelt area
A region of cortex, lateral and adjacent to the belt area, where neurons respond to more complex characteristics of sounds, as well as to input from other senses.
psychoacoustics
The branch of psychophysics that studies the psychological correlates of the physical dimensions of acoustics in order 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; also applies to perceived brightness which depends on the duration of light.
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; analogous to white light in vision for which all wavelengths are present.
critical bandwidth
The range of frequencies conveyed within a channel in the auditory system.
conductive hearing loss
Hearing loss caused by problems with the bones of the middle ear.
otitis media
Inflammation of the middle ear, commonly in children as a result of infection.
otosclerosis
Abnormal growth of the middle-ear bones that causes hearing loss.
sensorineural hearing loss
Hearing loss due to defects in the cochlea or auditory nerve.
