Lecture 4 Flashcards
Perception and the interpretation of sounds
echo-location
helps to navigate through the world -> creating a 3D image
people born blind
occipital lope adapts to use other senses
Neuroplasticity
hearing is related to touch
touch =. sensitivity to pressure on the skin
hearing = sensitivity to pressure on a specific tissue of the ear
What is sound?
the vibration of air produced by actions of an object
the vibrations move outwards from the sound source in a way that can describe as a wave
amplitude
the height of the sound wave
indicates the pressure exerted by the molecules of air as they move back and forth
the loudness of sound
frequency
the rate at which molecules of air move back and forth
the pitch, number of complete waves per second
transformations
physical waves transform into electrical signals to be processed by any neurones
sound has different qualities
evolution can therefore use sound in different ways
evolution of sound
elephants use low frequency sounds for communications - sounds humans can’t detect
individual differences
cognition isn’t a fixed concept
males 85 - 180 Hz and females 165 - 255 Hz
outer ear
amplifier - acts as a funnel, receiving sound waves and sending them inwards
consist of the pinna, the flaps of skin and cartilage and the auditory canal, the opening in the ear
vibrations in the air, causes the air in the auditory canal to vibrate, which then causes the eardrum to vibrate
middle ear
consist of three tiny bones and vibrations of the ear drum vibrate the bones which push against the oval window
amplifies the pressure of the received sound waves, so that transduction can occur
the oval window
a smaller area than the ear drum, the pressure on it ossicles greater than the pressure received by the eardrum
the inner ear
consists of the cochlea
contains the basilar membrane, which runs along the length of the cochlea
the basilar membrane is full of tiny hair cells. these hair cells, which act like touch receptors on the skin, connect to neurones whose axons form the auditory nerve
the auditory nerve transmits impulses to the brain areas responsible for hearing
conduction deafness
amplification failures
occurs when the bones connected to the eardrum fail to transmit sounds to the cochlea
can be connected with surgery removing whatever is obstructing the bones movement
people with conduction deafness still hear their own voice because it is conducted through the skull bones to the cochlea, bypassing the middle ear
nerve deafness
wear and tear
results from damage to the cochlea, hair cells, or auditory nerve
disease, heredity, and exposure to loud noises
hearing aids compensate for hearing loss, but only to some extent
in older adults, long term hearing loss can cause brain areas receiving certain frequencies to deteriorate due to inadequate input
lose the capacity to discriminate against different sound levels
Bekesy
discovered how pitch is perceived
sound waves entering the cochlea set up ‘traveling waves’ on the membrane, from the nearest end towards the far ed
high frequencies
produce waves that travel short distances
low frequencies
produce waves that travel longer differences
high pitch perception
firing neurones at the near end of the basilar membrane accompanied by little to no firing of neutrons at the far end
low pitch perception
firing of neurones from the distant end of the basilar membrane
asymmetry in auditory masking
the ability of one sound to prevent the hearing of another sound
low frequency sounds can mask high frequency sounds
the basilar membrane is sensitive to different frequencies at different parts
loss of hearing as we get older
we lose sensitivity to high frequency sounds more than low frequency sounds
due to
wearing out of the hair cells with repeated use, especially when working in noisy environments
why loss of hearing of high pitch sounds?
all sounds, high and low frequency, pass through the near end of the basilar membrane, which is sensitive to high frequency sounds. so the hair cell there wear out more than the cells further down the membrane
pitch perfect
individual differences
some people can hear a sound an detect the pitch straight away
different languages
‘tonal’ languages
different tones have different meanings
nurture
hearing allows us to…
localise sounds
determine what is out there
communicate with other humans
sound localisation
when we ‘hear’ the activity happens in our ears
but we perceive the sound as happening ‘out there’ and we can usually localise it
cues for sounds localisation
inter aural time differences
inter aural intensity differences
inter aural time differences
the time differences when sound waves reach one ear compared to the other
if a sound comes from straight ahead, the waves will reach both ears at the same time
but if the sound comes from, the right for example, the sound will reach the right ear a few fractions of a second earlier than the left ear
inter aural intensity differences
sounds are more intense at the ear closest to the source of sounds, because the head blocks partially blocks the pressure waves from reaching the opposite ear
the head blocks high frequency sounds more effectively than low frequency sounds
sound localisation
judging distance
as sound grows louder = perceive sounds as coming closer
two sounds differ in pitch = higher pitched frequencies carry better over further distances
echos
reverberation is the only cue for absolute distance os the amount of reverberation
in a closed room, you first hear the sound waves the source and then the waves reflected off other objects
many echos = the sound is coming from far away
it is hard to localise sound sources in a noisy room where echos are harder to hear
three directions we can judge sound location
left - right (azimuth)
distance
up - down (elevation)
mono aural sound localisation cues
uses information from one ear
the pinna and the head affect the intensities of the frequencies
auditory scene analysis
process by witch sound sources in the auditory scene are separated into individual perceptions
heuristics help to perceptually organise stimuli
onset time - sounds that starts at different times are likely to come from different sources
location - a single sound source tends to come from one location and move continuously
similarity of timbre and pitch - similar sounds are grouped together
phonemic restoration effect
the illusion whereby people hear phonemes that have been deleted, as if they were still there
direct sound
sound that reaches the listeners ear straight from the source
indirect sound
sound that is reflected off of environmental surfaces and then to the listener
precedence effect
when there is a delay in sound, listeners hear the sounds as only coming from the louder speaker
we perceive the sounds as coming from the source that reaches our ears first
