Basic physiology of the ear The cochlea - oval window

The cochlear is filled with a watery liquid that moves in response to the vibrations coming from the middle ear oval window - membrane covering opening in the cochlea - the stapes is attached directly to oval window (where the vibrations get into the cochlea - much smaller than eardrum - size difference further helps amplify sounds waves

2. Hearing Flashcards by Alecia Yu

Nature of sound:

sound caused by…

That are characterised by…

simplest sound wave is…

air pressure waves

amplitude (dB) - loudness
Frequency (Hz) - pitch
Phase - position within a cycle

a pure tone - sine wave

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Nature of sound:

sound caused by…

That are characterised by…

simplest sound wave is…

air pressure waves

amplitude (dB) - loudness
Frequency (Hz) - pitch
Phase - position within a cycle

a pure tone - sine wave

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human hearing range is …

20-20,000 Hx

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Typical vocal range…

80-1100Hx

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Nature of sound:

complec sounds can be built up from…

a series of sine waves with varying amplitudes, frequency and phase

can be decomposed into components by Fourier analysis

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Nature of sound:

what is the fundamental?
What are complex sounds made up of?

fundamental = lowest frequency component of a complex sound

many complex sounds are made up of harmonics, - integer multiples of the fundamental

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Basic physiology of the ear

components of the OUTER EAR

Pinna

increases the sound amplitude
Helps determine the direction from which a sound is coming form

External auditory canal

provides protection
increases the sound amplitude

Eardrum (tympanic membrane)
- vibrates in response to sound waves
Moves bones in the middle ear

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Basic physiology of the ear

Components of the MIDDLE EAR

ossicles

Malleus
Incus
Stapes

smallest bones of human body

ossicles transmit the vibrations of the eardrum in to the cochlea through lever actions

They also provide protection against high amplitude sounds
- muscles attached to the ossicles restrict the bones’ movements

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Basic physiology of the ear

components of the INNER EAR

semicircular canals
- important for vestibular sense (sense of orientation)

Cochlea
- contains auditory sensory receptors

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Basic physiology of the ear

The cochlea

oval window

The cochlear is filled with a watery liquid that moves in response to the vibrations coming from the middle ear

oval window

membrane covering opening in the cochlea
the stapes is attached directly to oval window (where the vibrations get into the cochlea
much smaller than eardrum - size difference further helps amplify sounds waves

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Basic physiology of the ear

The cochlea canals

three canals of the cochlear

vestibular canal
tympanic canal
cochlear duct

separated by

Reissner’s membrane
basilar membrane (on which hair/auditory receptor cells located in cochlear duct)

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Basic physiology of the ear

The cochlea canal and membrane orientation/order

vestibular canal
> Reissner's membrane 
>> cochlear duct 
>>> Basilar membrane
>>>>Tympanic membrane

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Basic physiology of the ear

vibrations to neural signals. HOW?

the three membranes vibrate in response to vibrations of the oval window

Wen the basilar membrane vibrates, hair cells are also set in motion

converts the vibrations in to neural signals

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the auditory cortex

What auditory tasks can be performed without the auditory cortex present?

onset of sound
changes in sound intensity
Changes in sound frequency

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Typical vocal range…

80-1100Hx

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Nature of sound:

complec sounds can be built up from…

a series of sine waves with varying amplitudes, frequency and phase

can be decomposed into components by Fourier analysis

How well did you know this?

Not at all

Perfectly

Nature of sound:

what is the fundamental?
What are complex sounds made up of?

fundamental = lowest frequency component of a complex sound

many complex sounds are made up of harmonics, - integer multiples of the fundamental

Basic physiology of the ear

components of the OUTER EAR

Pinna

increases the sound amplitude
Helps determine the direction from which a sound is coming form

External auditory canal

provides protection
increases the sound amplitude

Eardrum (tympanic membrane)
- vibrates in response to sound waves
Moves bones in the middle ear

Basic physiology of the ear

Components of the MIDDLE EAR

ossicles

Malleus
Incus
Stapes

smallest bones of human body

ossicles transmit the vibrations of the eardrum in to the cochlea through lever actions

They also provide protection against high amplitude sounds
- muscles attached to the ossicles restrict the bones’ movements

Basic physiology of the ear

components of the INNER EAR

semicircular canals
- important for vestibular sense (sense of orientation)

Cochlea
- contains auditory sensory receptors

Basic physiology of the ear

The cochlea

oval window

The cochlear is filled with a watery liquid that moves in response to the vibrations coming from the middle ear

oval window

membrane covering opening in the cochlea
the stapes is attached directly to oval window (where the vibrations get into the cochlea
much smaller than eardrum - size difference further helps amplify sounds waves

Basic physiology of the ear

The cochlea canals

three canals of the cochlear

vestibular canal
tympanic canal
cochlear duct

separated by

Reissner’s membrane
basilar membrane (on which hair/auditory receptor cells located in cochlear duct)

Basic physiology of the ear

The cochlea canal and membrane orientation/order

vestibular canal
> Reissner's membrane 
>> cochlear duct 
>>> Basilar membrane
>>>>Tympanic membrane

Basic physiology of the ear

vibrations to neural signals. HOW?

the three membranes vibrate in response to vibrations of the oval window

Wen the basilar membrane vibrates, hair cells are also set in motion

converts the vibrations in to neural signals

Central auditory pathways nerve fibres from each cochlear synapse in a number of sites on the way to the primary cortex the pathway is...

``` The cochlear > The cochlear nucleus >> The superior olivary nucleus >>> The inferior colliculus >>>> The medial geniculate nucleus ``` NOTE: signal at cochlear nucleus splits and goes to each of the superior olivary nuclei > beyond this point, input from both ears is present in both hemispheres

auditory space perception basilar membrane does not directly indicate sound locations so How is auditory space percived?

it is a biaural process - interaural time different >>onset difference >> phase difference - interaural intensity difference

the auditory cortex comparing auditory jask abilities with and without the cortex, What can be concluded

the cortex deals with more complex auditory tasks while the lower structures deal with simple aspects of sound speech perception requires structures beyond the primary auditory cortex

theories of encoding how do auditory system isolate and identify the frequencies of sounds. HOW?

basilar membrane is 30mm long with varying stiffness and widths along its length. Traveling waves move along the basilar membrane and peak at different points depending on the frequency of the sound Thus the location of the peak identifies the frequency of the sound stimulating auditory nerves at different cochlear locations leads to perception of sound in different pitch

theories of encoding Who suffers from frequency specific hearing loss?

people who have damage to specific parts of the cochlea

theories of encoding what are tonotopic maps?

maps present in the auditory system depict how auditory neurons are arranged in an orderly manner

pitch perception monoaural encoding refers to...

how sound frequency is encoded in each ear i.e. cochlear nucleus pathway

pitch perception biaural pitch encoding refers to...

how structures beyond the cochlear nucleus should be contributing to pitch perception missing fundamental can be perceived when harmonics are presented in one ear and can also be receive when presented in different jars

Loudness perception what are the basic mechanisms of loudness perception

overall firing rate range of firing

Loudness perception what factors affect loudness perception

sound duration - longer=louder frequency

Loudness perception how does frequency effect loudness

generally higher frequencies are perceived to be louder as amplitude increases the effect of frequency becomes smaller

auditory space perception in auditory space perception, you try to determine a sound's...

horizontal direction (azimuth) vertical direction distance

auditory space perception describe interaural time diference

unless a sound is directly in front or behind, it reaches two ears at different times (onset difference) > detected by a simple "delay line" mechanisms in brain same sound will most likely be in two different phases when it reaches each ear (Phase difference) > but the phase difference is less useful for localising high-frequency sounds

auditory space perception describe inter aural intensity diference

the same sound should be a bit more intense at the eat that is closer to the sound source > the energy of a sound decreases as it travels farther > the head works as a barrier that reduces the intensity of the sound (sound shadow) >> this effect is more pronounced for high frequency sounds

auditory space perception How does frequency effect auditory space perception

interaural time difference (phase) is useful for localising low frequency sounds interaural intensity difference is useful for localising high frequency sounds

auditory space perception How is head movement useful for auditory localisation

by changing the position of the ears you can experience changes in interaural time/intensity differences