hearing Flashcards
what is a sound?
- Sound arises from the movement of vibrations of an object
- This triggers a soundwave/movement which squeezes air molecules together and pulls them apart
- This pressure wave travels and spreads outwards from the source to the listener.
what is the y and x axis of a waveform and how is it presented ?
y axis = amplitude
x axis = time
as a wave
what is the y and x axis of a spectrogram and how is it presented ?
y axis = frequency
x axis = time
as a line
what is amplitude?
the intensity or loudness of a sound
what is period of a wave ?
it is the frequency/pitch of a wave
how is pitch expressed
as hertz (Hz) this is the number of a time a period is repeated every second
what does complexity of a sound refer to?
its timbre
how is loudness measured?
in decibels
explain the decibel scale
starting at 0 is the human threshold up to 140 which would really hurt a person ears (airplane taking off)
what is timbre?
timbre is the difference between a sound that has the same pitch and loudness
for timbre a sound must be complecx and have various tones
what does each complex tone have?
a fundamental tone
multiple frequencies referred to as harmonics
do harmonics in a compex tone have to have the same amplitude?
no
what is the relationship between the fundamental harmonic and the other harmonics in a complex tone?
the other harmonics are a multiple of the fundamental tone
so if the fundamental tone has Hz of 200 the second harmonic will be 400 Hz
areas of the ear
outer
middle
inner
outer ear name
pinna
describe the middle ear
- the middle ear is air filled
- three bones called ossicles
- ear drum
- equalises pressure betwen the middle ear and the outside
how do the three ossicles function
they are attached as a lever hitting the ear drum with vibrations which then need to be replicated by the cochlea
describe the cochlea
its a spiral shaped system that is fluid filled within the inner ear
what do the ossicles do to vibrations
they have to amplify sounds we hear by 20x so that the cochlea can replicate the sound. this is because the cochlea is fluid filled it needs louder vibrations to replicate
what is the stapedial reflex
muscular reflex in the ear which contracts the bones to come away from the oval window so that the loud vibrations aren’t amplified before going to the cochlea which prevents damage.
what is the basilar membrane?
strip of flesh - vibrates when the stapes (3rd bone) moves the fluid in the ear - narrow at base and wide at the apex (floppy and thin) the bottom vibrates with high frewuncy sounds the top is low frequency
the top of the basilar membrane vibrates with what frequencies?
low frequencies
the cochlea acts as a
- frequency analyser, converts enegrgy at different frequencies into neural activity in different fibres of the auditory nerve
- top is the chamber sound goes up theres a hole then into the bottom chamber.
what is the organ of corti?
- sits on top of the basilar membrane
- full of neurons and sensory cells
- one row of inner hair cells and 3 rows of outer hair cells
what od the outer hair cells of the organ of corti do?
outer hair cells - put energy into the basilar membrane and amplify sounds
what do the inner hair cells of the organ of corti do?
detect the movement of the basilar membrane
tectorial membrane
inner hair cells are crushed against and bent this may trigger an actjon potential.
what is the cochlear nucleus
a relay struction in the brain stem - sends neural activity to other nuclei in brain stem for analysis. last station where ears are independent.
what is the superior olive?
merges the ear together, analyses the location of the sound.
what dopes the primary auditory area in the cerebral cortex do?
nalyses higher-order features of sounds, including their spectral shape. This happens later in auditory pathway than analyses of location and pitch because it is less reliant on precise timing.
what is frequency selectivity?
- the ability to separate sounds with different frequencies that occur at the same time.
- when sounds have a similar timbre it is difficult to sperate them because they activate a similar area of the basilar membrane.
what is laser interferometry?
measures the basilar membrane selectivity by placing a tiny glass bead on the basilar membrane of an anaesthetised animal and then beams a lazer on the glass ball. then play different tones and measures its vibrations and motion.
psychoacoustic demonstration of frequency selectivity
tight headphones if they can hear a tone.
play tone with background noise and see at what point they can discriminate from two frequencies.
How close can the noise be to the target frequency for us to hear them seperatley?
this can be researched in the lab psychoacoustically
test tone at a fixed level
masker tone you have to ignore - this will be maniuplated so taht its impossiblw for u to hear the test tone
adjusted until we cant heat test tone
test = 4000Hz
the closer the masker is to the frequency tone, the lower the level of the masker needed to mask the test tone.
how does frequency selectivity benefit speech?
sounds are so similar but because we can detect the diffrent pitches it allows us to know what is being said.
frictivie sounds have higher frequencies for example
what is mimiumum of a speech sound we need to here to disginuish between two speech sounds
- we only need to hear the first and second formant of a sound for our basilar membrane to distinguish between sounds
what is a formant
the amplified (peaks) of frequencies within a vowel
what is the bottom up effect of hearing
basilar membrane etc
what are the five top down effects on hearing?
Ganong effect, phoneme restoration, sound and word reduction, sinewave speech and McGurk effect.
what is the ganong effect and example?
the tendency to hear an ambigous word as a word we already know effect of lexical knowledge on phoneme identification
play g - k on a continuimm
if sound is g theyll get 0% k responses but this increases as you go
but if you add iss to the end of the letters hearing the k starts earlier bc kiss is a word not giss.
what is phoneme restoration?
when we trick our auditory system into hearing a word we exepect even if it is said wrong.
e.g., approximatley without the l we would still hear the full word
sound and word reduction
words can be acoustically reduced but we have semantic expectations and can hear words
McGurk effect
our audiorty information changes as to what is in the visual
sound says bah but a person looks at someone saying fah and we believe theyre saying bah and that’s what we hear