week 8 - anatomy of the ear Flashcards
condensation
- increase in pressure
- molecules are closer to each other
rarefaction
- decrease in pressure
- molecules are further from each other
What are the physical aspects of sound?
- amplitude
- frequency
amplitude
- size of pressure wave
- high amplitude = loud
- low amplitude = quiet
frequency
- number of cycles per second
- high frequency = high pitch
- low frequency = low pitch
What are the perceptual aspects of sound?
- loudness
- pitch
- timbre
loudness
- the perceptual quality most closely related to amplitude
- measured in decibels
pitch
the perceptual quality we describe as high/low
timbre
- all other perceptual aspects of sound
- ex.) being able to tell the difference between two instruments
outer ear
contains pinna and external auditory canal
pinna
contributes to sound localization
external auditory canal
tube filled with protective hair and wax
middle ear
includes the tympanic membrane, ossicles, and oval window
tympanic membrane
- border between middle and outer ear (ear drum)
- vibrates at the same frequency of sound coming in
- allows our ossicles to vibrate
ossciles
- vibrate at a higher intensity to knock oval window and move fluid behind it
- hammer -> anvil _> stirrup
oval window
membrane-covered opening between middle and inner ear that knocks at fluid inside cochlea
inner ear
contains the cochlea
cochlea
contains 3 tubes
- scala vestibuli
- scala media
- scala tympani
Which cochlear tube does reception occur through hair cells (cilia) and has the most action take place?
scala media
How does cilia activate transduction?
- cilia must move in a certain direction in order to open to open ion channels
- opening of cilia allows calcium to move inside cell and activate an action potential
- action potential = transduction
How do neurons make up for nerve firing to a sound stimulus during refractory periods?
- multiple neural responses are needed in order to encompass all frequencies
- creates a cranial nerve
cranial nerve
collection of nerve fibers
What two theories are believed to code for pitch perception?
- frequency theory
- place theory
frequency theory
- basiliar membrane vibrates in synchrony with sound
- auditory nerve produces action potential at the same frequency
What are the physical properties of the basilar membrane?
narrow up until apex where it is the thickest
place theory
- frequency of sound is indicated by the place along the basilar membrane
- each area is tuned to a specific frequency
auditory space
surrounds an observer and exists wherever there is sound
Azimuth coordinates
- left-right
elevation coordinates
- up-down
distance coordinates
position from observer
binaural cue
location cues based on the comparison of the signals by the left/right ears
interaural time difference (ITD)
- no differences in time when distance to each ear is the same
- time differes when source is one one side of the observer
internaural level difference (ILD)
- difference in air pressure
- if sound is louder in one ear, sound is most likely coming from that side
monaural cue
- uses information from one ear
- reliant on pinna
Describe the pinna experiment on monaural cues
- microphones were placed in ears to measure how sound bounces off location of ear
- different sound in different locations (above vs. below aka elevation)
spectral cues
elevation coordinate, especially at higher frequencies
spectral cues experiment
- molds were placed in ears to measure spectral cues for a period of time
- brain gets used to mold over time; performance high after removal
- suggests there are two sets of neurons - one for each set of cues
What type of cues work best for azimuth coordinate?
ITDs and ILDs
What type of cues work best for low frequencies?
ITD
What type of cues work best for high frequencies?
ILD
