4.2

envelope of the traveling wave

A curve that indicates the maximum displacement at each point along the basilar membrane caused by a traveling wave

cochlear implant

A device in which electrodes are inserted into the cochlea to create hearing by electrically stimulating the auditory nerve fibers. This is used to restore hearing in people who have lost their hearing because of damaged hair cells.

presbycusis

A form of sensorineural hearing loss that occurs as a function of age and is usually associated with a decrease in the ability to hear high frequencies. Since this loss also appears to be related to exposure to environmental sounds, it is also called sociocusis.

superior olivary nucleus

A nucleus along the auditory pathway from the cochlea to the auditory cortex. This receives inputs from the cochlear nucleus.

inferior colliculus

A nucleus in the hearing system along the pathway from the cochlea to the auditory cortex. This receives inputs from the superior olivary nucleus.

cone of confusion

A surface in the shape of a cone that extends out from the ear. Sounds originating from different locations on this surface all have the same interaural level difference and interaural time difference, so information provided by these cues is ambiguous.

medial geniculate nucleus

An auditory nucleus in the thalamus that is part of the pathway from the cochlea to the auditory cortex. This receives inputs from the inferior colliculus and transmits signals to the auditory cortex.

tonotopic map

An ordered map of frequencies created by the responding of neurons within structures in the auditory system. There is a _____ of neurons along the length of the cochlea, with neurons at the apex responding best to low frequencies and neurons at the base responding best to high frequencies

inner hair cell

Auditory receptor cell in the inner ear that is primarily responsible for auditory transduction and the perception of pitch

outer hair cell

Auditory receptor cells in the inner ear that amplify the response of the inner hair cells

phase locking

Firing of auditory neurons in synchrony with the phase of an auditory stimulus

sensorineural hearing loss

Hearing loss caused by damage within the inner ear.

conductive hearing loss

Hearing loss that occurs when the vibrations of a sound stimulus are not conducted normally from the outer ear into the cochlea

cochlear amplifier

How movement of the outer hair cells in response to sound increases basilar membrane vibration and therefore amplifies the response of the inner hair cells

azimuth coordinate

In hearing, specifies locations that vary from left to right relative to the listener.

spectral cue

In hearing, the distribution of frequencies reaching the ear that are associated with specific locations of a sound. The differences in frequencies are caused by interaction of sound with the listener's head and pinnae.

pitch neurons

Neurons that respond to stimuli associated with a specific pitch. These fire to the pitch of a complex tone even if the first harmonic or other harmonics of the tone are not present.

effect of the missing fundamental

Removing the fundamental frequency and other lower harmonies from a musical tone does not change the tone's pitch

auditory stream segregation

The effect that occurs when a series of tones that differ in pitch or timbre are played so that the tones become perceptually separated into simultaneously occurring independent streams of sound.

precendence effect

The effect that occurs when two identical or very similar sounds reach a listener's ears separated by a time interval of less than about 50 to 100 ms, and the listener hears the sound that reaches his or her ears first.

interaural level difference (ILD)

The greater level of a sound at the closer ear when a sound source is positioned closer to one ear than to the other. This effect is most pronounced for high-frequency tones. This provides a cue for sound localization.

cochlear nucleus

The nucleus where nerve fibers from the cochlea first synapse.

pinnae

The part of the ear that is visible on the outside of the head.

place theory of hearing

The proposal that the frequency of a sound is indicated by the place along the organ of Corti at which nerve firing is highest. This is based on Bekesy's traveling wave theory of hearing.

acoustic shadow

The shadow created by the head that decreases the level of high-frequency sounds on the opposite side of the head. This is the basis of the localization cue of interaural level difference.

reverberation time

The time it takes for a sound produced in an enclosed space to decrease to 1/1000th of its original pressure.

interaural time difference (ITD)

When a sound is positioned closer to one ear than to the other, the sound reaches the close ear slightly before reaching the far ear, so there is a difference in the time of arrival at the two ears. This proves a cue for sound localization.