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 spectrum and how is it presented ?
y axis = amplitude
x axis = frequency
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
- inner one row of hair cells and 3 rows of V outer hair cells
what od the outer hair cells of the organ of corti do?
put energy back into the basilar membrane, these are elastic and move with membrane amplifying it. more likely to not hear a sound because vibration wont be as loud.
what do the inner hair cells of the organ of corti do?
detect and amplify the movement of the basilar membrane