Chapter 9: Hearing: Physiology and Psychoacoustics Flashcards
amplitude or intensity
The magnitude of displacement (increase or decrease) of a sound pressure wave. Amplitude is perceived as loudness.
frequency
For sound, the number of times per second that a pattern of pressure change repeats. Frequency is perceived as pitch.
hertz (Hz)
A unit of measure for frequency. One hertz equals one cycle per second.
loudness
The physiological aspect of sound related to perceived intensity (amplitude).
pitch
The psychological aspect of sound related mainly to perceived frequency.
decibel (dB)
A unit of measure for the physical intensity of sound. Decibels define the difference between two sound as the ratio between two sound pressures. Each 10:1 sound pressure ratio equals 20 dB, and a 100:1 ratio equals 40 dB.
sine wave or pure tone
A 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 ear.
ear canal
The canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage tot he tympanic membrane.
Tympanic membrane (eardrum)
The eardrum; a thin shit of skin at the end of the outer ear canal. The tympanic membrane vibrates in responds to sound.
outer ear
The external sound-gathering portion of the ear, consisting of the pinna and the ear canal.
middle
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.
ossicle
Any of three tiny bones of the middle ear: malleus, incus, and stapes.
malleus
One of the three ossicles, receives vibration from the tympanic membrane and is attached to the incus.
incus
The middle of the three ossicles connecting malleus to stapes.
Stapes
Third ossicle. Connects to incus and presses against oval window of cochlea.
oval window
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside.
inner ear
A hollow cavity in the temporal bone of the skull, and the structures within the cavity: the cochlea and the semicircular canals of the vestibular system.
tensor tympani
The muscle attached to the malleus; tensing the tensor tympani decreases vibration.
stapedius
The muscle attached to the stapes. Tensing the steapedius decreasese vibration,
acoustic reflex
A reflex that protects the ear from intense sounds, via contraction of the stapedius and tensor tympani muscles.
cochlea
A spiral structure of the inner ear containing the organ or Corti.
tympanic canal
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.
vestibular canal
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.
middlew canal
One of three fluid filled passages in the cochlea. The middle canal is in between vestibular/tympanic canals at apex of cochlea.
helicotrema
The opening that connects the tympanic and vestibular canals at the apex of the cochlea
Reisnner’s membrane
A thin sheath of tissue separating vestibular and middle canals in 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 the tympanic canal that releases excess pressure remaining from extremely intense sounds.
organs of Corti
A structure on the basilar membrane of the cochlea that is compose of hair cells and dendrite pf auditory nerve fibers. Translates movements of cochlear partition into neural signals.
hair cell
Any cell that has stereocilia for transducing mechanical movements in inner ear into neural activity sent to the brain; some hair cells also receive inputs from the brain.
auditory nerve fiber
A collection of neurons convey info from hair cells in cochlea to and from brain stem.
stereocilium
Any of the hairlike extensions on the tips of the 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 middle canal, 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 CNS.
efferent fiber
A neuron that carries info from CNS to periphery.
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.
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 a steady intensity.
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 to at increasing intensities.
low-spontaneous fiber
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.
high-spontaneous fiber
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.
mid-spontaneous fiber
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 love and high spontaneous fibers.
phase locking
Firing 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.)
temporal code
Turing of different parts of the cochlea to different frequencies, in which info about the particular frequency of an incoming sound wave is coded by the timing of neural firing as it related 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 done 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 both 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 info.
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 regions of cortex, lateral and adjacent to the belt area, where the neurons respond to more complex characteristics of sound, as well as to input from other senses.
psychoacoustics
The study of the psychological correlates of the physical dimensions of acoustics; branch of psychophysics.
audibility threshold
The lowest sound pressure level that can be reliable detected at a given frequency.
equal-loudness curves
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.
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. White noise in hearing is 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.
ototoxic
Producing adverse effects on cochlear or vestibular organs or nerves.
