perception 4 Flashcards
what is the perceptual definition of sound?
sound is the experience we have when we hear
what is the physical definition of sound?
sound is pressure changes in the air or other medium caused by the vibration of an object
what is a pure tone?
when changes in air pressure form a perfect sinuoidal wave
what is amplitude?
size of the variation in air pressure
what is amplitude related to perception of?
loudness
what is frequency?
the number of cycles per second
what is frequency related to perception of?
pitch
what are complex sounds?
combinations of different sine waves
what do natural sounds consist of?
fundamental frequency with harmonics
what are the three sub divisions of the ear?
outer, middle and inner
what does the outer ear consist of?
pinnae
auditory canal
tympanic membrane (eardrum)
what is the pinnae?
visible external parts of the ear
what is the auditory canal?
tube-like structure which protects the middle ear
what is the tympanic membrane?
cone shaped membrane which separates the outer and middle ear
how do sound waves affect the tympanic membrane?
cause a pressure difference= vibration
what do larger amplitude sounds result in?
larger vibrations
what do higher frequency sounds result in?
faster vibrations
what does the middle ear consist of?
small cavity containing the ossicles (smallest bones in human body)
what are the ossicles?
malleus (hammer)
incus (anvil)
stapes (stirrup)
what do the ossicles do?
amplify the vibrations of the tympanic membrane
transmit them to the inner ear at the oval window
what is the main structure in the inner ear?
cochlea
what does the cochlea do?
vibration displaces its fluid
=change in pressure which spreads across the spiral structure
what are the three canals the cochlea consists of?
vestibular
middle
tympanic
which membrane triggers auditory transduction?
basilar membrane
what is auditory transduction?
transformation of sound waves to electrical energy, by the Organ of Corti
how is a voltage generated in auditory transduction
sensitive specialised hair cells in the Organ of Corti are bent
= impulses in auditory nerve cells are sent to the brain
what scale is amplitude measured on?
logarithmic scale in decibels
what is rate code? (loudness)
sound amplitude is coded in the firing rate of auditory nerve fibres
how do we discriminate loudness?
increase in sound intensity= increase in auditory nerve rate intensity
some fibres- high spontaneous rates, saturate rapidly
some fibres- low spontaneous rates, saturate slowly
what does loudness depend on?
amplitude
frequency
what range of pitches can humans hear between?
20Hz and 20,000Hz
what is place code? (pitch)
sound frequencies cause vibration in specific areas along the basilar membrane
where do low frequencies cause vibrations?
near the apex
where do high frequencies cause vibrations?
near the base
what is timing code? (pitch)
frequnecy depends on which auditory nerve fibres respond and when they respond
what is phase locking?
auditory nerve responses are synchronised according to changes in pressure, up to 4000Hz
what is pitch determined by?
frequency of a sound
what is timbre determined by?
number, frequency and amplitudes of harmonics
what is the missing fundamental illusion?
we continue to perceive a pitch as consistent with a missing fundamental frequency
what does the missing fundamental illusion suggest?
brain also infers missing fundamentals- not just determined in cochlea (top down process)
