week 5: hearing Flashcards
what is sound caused by
changes in air pressure
what are pressure waves characterised by
amplitude
frequency
phase
what is phase in pressure waves
position within a cycle
what is amplitude in pressure waves
related to loudness
decibels: dB
what is frequency in pressure waves
related to pitch
hertz: Hz
what is the simplest sound wave
a pure tone sine wave
what is the human hearing range
20-20000 Hz
what is the range most things are heard
80-1100 Hz
how are complex sounds built
from series of sine waves from varying amplitude, frequency, and phase
how do we decompose complex sounds into their sine wave components
a method called fourier analysis
what is The lowest frequency component of a complex sound is called
fundamental
components of the outer ear
pinna
external auditory canal
eardrum
what does the pinna do
increase the sound amplitude
helps determine the direction from which a sound is coming
what does the external auditory canal do
provides protection
increases the sound amplitude
what does the eardrum do
vibrates in response to sound waves
moves bones in the middle ear
what is the component and its component in the middle ear
ossicles:
- malleus
- incus
- stapes
what is the smallest bone in the human body
the ossicles (malleus, incus, stapes)
what do the ossicles do
transmit the vibration of the eardrum with some amplification into the choclea through lever actions
provide protection against high amplitude sounds
how do the ossicles provide protection against high amplitude sounds
muscles attached to the ossicles restrict the bones movements
the inner ear consists of
cochlea
what do the cochlea contain
auditory sensory receptors
what is the cochlea filled with
liquid, which moves in response to the vibrations coming from the middle ear
what are the 3 canals in the cochlea
vestibular canal
tympanic canal
cochlear duct
what are the inner ear canals separated by
reissners membrane
basilar membrane
where are auditory receptor cells (hair cells) located
basilar membrane in the cochlear duct
what do the reissners membrane and basilar membrane do
they vibrate in response to vibrations of the oval window
what happens when basilar membrane vibrates
hair cells are also set in motion and this converts the vibration into neural signals
Nerve fibres from each cochlea synapse in a number of sites on the way to the primary auditory cortex. What are these sites
the cochlear nucleus
the superior olivary nucleus
the inferior colliculus
the medial geniculate nucleus
what does the signal that arrive at the cochlear nucleus do
the signal arriving at the cochlear nucleus splits and goes to each of the superior olivary nuclei. Beyond this point, input from both ears is present in both hemispheres
what tasks cannot be performed without the cortex
discriminating the pattern of several tones
discriminating the duration of sounds
localising sounds in space
what does speech perception require
structures beyond the primary auditoy cortex
what does the cortex deal with
the cortex deals with more complex auditory tasks while the lower structures deal with simple aspects of sounds
what identifies the frequency of a sound
the location of a peak
When people have damage to a specific part of the cochlea, they tend to suffer from
frequency-specific hearing loss
Stimulating auditory nerves at different cochlear locations leads to
perception of sounds in different pitch
what happens to hair cells at different points on the basilar membrane
Hair cells are tuned to different ranges of frequency according to the location along the basilar membrane
what happens if there is a missing fundamental
When higher-order harmonics are present in the absence of the fundamental (first harmonic), the missing fundamental is “filled in” and therefore is still perceived even when harmonics are presented to different ears
Binaural pitch encoding
Structures beyond the cochlear nucleus should be contributing to pitch perception
what are the 2 basic mechanisms for loudness perception
overall firing rates
range of firing
Factors that affect loudness perception
Sound duration (longer = louder)
Frequency
what type of sounds are perceived to be louder
higher frequency sounds (up to 5000Hz)
around 3000-5000Hz sounds are perceived to be the loudest
what happens when the amplitude goes up
the effect of frequency becomes smaller
In auditory space perception, you try to determine a sound’s
horizontal direction (azimuth)
vertical direction
distance
what provides more precise information about an objects location
vision
Why can we auditorily localize sounds at all?
Nothing on the basilar membrane directly indicates sound locations
what type of process is auditory space perception
binaural process
what is Interaural time difference
Unless a sound is directly in front of or behind you, it reaches two ears at different times (onset difference)
what impacts interaural time difference
onset difference
phase difference
what is meant by phase difference for interaural time difference
The same sound will most likely be in different phases when it reaches each of the two ears
what is the phase difference less useful for
localising high frequency sounds
how can the onset difference be detected for interaural time difference
by simple delay line mechanism in the brain
what is Interaural intensity difference
The same sound should be a bit more intense at an ear that is closer to the sound source
why is there an Interaural intensity difference
The energy of a sound decreases as it travels farther
the head works as a barrier that reduces the intensity of the sounds (sound shadow). this effect is more pronounced for high-frequency sounds
Interaural time difference (phase difference) is useful for
localizing low-frequency sounds
Interaural intensity difference is useful for localizing
high-frequency sounds
what works well for sounds in the middle range
neither cue works well for pure tones around 1000-3000Hz
what is the role of head movements
Head movements are generally helpful for auditory localization
By changing the positions of the ears, you can experience changes in interaural time/intensity differences
what direction do humans perceive sound better
horizontal directions better than vertical directions through auditory cues
why can humans perceive horizontal sound better
pinnae are more effective in distinguishing front/back than above/below
ear positions can be varied more freely along the horizontal dimension
Limits of auditory localisation
Most of the auditory localisation cues are dependent on the distance between a sound source and the ears. Because of this it is difficult to distinguish locations of sounds that are equidistant to an ear
Two cues for auditory distance perception
loudness
the energy ratio of direct and reverberant sound
where is The energy ratio of direct and reverberant sound not available
in open spacw
When we have auditory cues only, we
underestimate the distance to a sound source
what happens when we can visually perceive where a sound “should be” coming from
it tends to override our auditory localization
what happens When we have some visual information about how a stimulus “should” sound
it strongly affects how we hear the stimulus
what is vision good for
a good source of spatial information
what is audition good for
good source of temporal information
what does auditory information influence
Auditory information can influence our visual perception by providing conflicting temporal information
