The opening that connects the tympanic and vestibular canals at the apex of the cochlea.
The psychological aspect of sound related to perceived intensity (amplitude).
A gelatinous structure, attached on one end, that extends into the middle canal of the ear, floating above inner hair cells and touching outer hair cells.
An auditory nerve fiber that has a high rate (more than 30 spikes per second) of spontaneous firing; high-spontaneous fibers increase their firing rate in response to relatively low levels of sound.
A thin sheath of tissue separating the vestibular and middle canals in the cochlea.
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.
A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.
The study of the psychological correlates of the physical dimensions of acoustics; a branch of psychophysics.
The eardrum; a thin sheet of skin at the end of the outer ear canal. The tympanic membrane vibrates in response to sound.
One of three fluid-filled passages in the cochlea. The tympanic canal extends from the round window at the base of the cochlea to the helicotrema at the apex. Also called scala tympani.
For sound, the number of times per second that a pattern of pressure change repeats. Frequency is perceived as pitch.
Producing adverse effects on cochlear or vestibular organs or nerves.
The external sound-gathering portion of the ear, consisting of the pinna and the ear canal.
Inflammation of the middle ear, commonly in children as a result of infection.
Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency. (The neuron need not fire on every cycle, but each firing will occur at the same point in the cycle.)
sine wave or pure tone
A waveform for which variation as a function of time is a sine function.
One of the three ossicles. Connected to the incus on one end, the stapes presses against the oval window of the cochlea on the other end.
characteristic frequency (CF)
The frequency to which a particular auditory nerve fiber is most sensitive.
Noise consisting of all audible frequencies in equal amounts. White noise in hearing is analogous to white light in vision, for which all wavelengths are present.
The muscle attached to the stapes; tensing the stapedius decreases vibration.
An arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency.
The middle of the three ossicles, connecting the malleus and the stapes.
Any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitters.
A neuron that carries sensory information to the central nervous system.
One of three fluid-filled passages in the cochlea. The vestibular canal extends from the oval window at the base of the cochlea to the helicotrema at the apex. Also called scala vestibuli.
A reflex that protects the ear from intense sounds, via contraction of the stapedius and tensor tympani muscles.
A neuron that carries information from the central nervous system to the periphery.
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside.
A plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea.
A graph plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities.
The process by which a sound at a constant level is perceived as being louder when it is of greater duration. The term also applies to perceived brightness, which depends on the duration of light.
The first brain stem nucleus at which afferent auditory nerve fibers synapse.
A unit of measure for frequency. One hertz equals one cycle per second.
Abnormal growth of the middle-ear bones that causes hearing loss.
An early brain stem region in the auditory pathway where inputs from both ears converge.
An auditory nerve fiber that has a medium rate (10–30 spikes per second) of spontaneous firing. The characteristics of mid-spontaneous fibers are intermediate between low- and high-spontaneous fibers.
A tiny filament that stretches from the tip of a stereocilium to the side of its neighbor.
A spiral structure of the inner ear containing the organ of Corti.
amplitude or intensity
The magnitude of displacement (increase or decrease) of a sound pressure wave. Amplitude is perceived as loudness.
The psychological aspect of sound related mainly to perceived frequency.
A hollow cavity in the temporal bone of the skull, and the structures within this cavity: the cochlea and the semicircular canals of the vestibular system.
Using a second sound, frequently noise, to make the detection of another sound more difficult.
threshold tuning curve
A graph plotting the thresholds of a neuron or fiber in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response.
The canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane.
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.
medial geniculate nucleus
The part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex.
The point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate.
The outer, funnel-like part of the ear.
sensorineural hearing loss
Hearing loss due to defects in the cochlea or auditory nerve.
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.
Any of three tiny bones of the middle ear: malleus, incus, and stapes.
The lowest sound pressure level that can be reliably detected at a given frequency.
The muscle attached to the malleus; tensing the tensor tympani decreases vibration.
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.
organ of Corti
A structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers.
A unit of measure for the physical intensity of sound. Decibels define the difference between two sounds as the ratio between two sound pressures. Each 10:1 sound pressure ratio equals 20 dB, and a 100:1 ratio equals 40 dB.
An auditory nerve fiber that has a low rate (less than 10 spikes per second) of spontaneous firing; low-spontaneous fibers require relatively intense sound before they will fire at higher rates.
One of three fluid-filled passages in the cochlea. The middle canal is sandwiched between the tympanic and vestibular canals and contains the cochlear partition. Also called scala media.
A map plotting the firing rate of an auditory nerve fiber against varying frequencies at a steady intensity.
auditory nerve fiber
A collection of neurons that convey information from hair cells in the cochlea to (afferent) and from (efferent) the brain stem.
The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency.
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.
The lowest-frequency component of a complex periodic sound.
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.
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.
An air-filled chamber containing the middle bones, or ossicles. The middle ear conveys and amplifies vibration from the tympanic membrane to the oval window.
A soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds.
conductive hearing loss
Hearing loss caused by problems with the bones of the middle ear.
The range of frequencies conveyed within a channel in the auditory system.
primary auditory cortex (A1)
The first area within the temporal lobes of the brain responsible for processing acoustic information.
The combined basilar membrane, tectorial membrane, and organ of Corti, which are together responsible for the transduction of sound waves into neural signals.
A midbrain nucleus in the auditory pathway.
A representation of the relative energy (intensity) present at each frequency.
One of the three ossicles. The malleus receives vibration from the tympanic membrane and is attached to the incus.
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.