hearing Flashcards
what is relationship between compression and rarefaction?
an oscillating object will cause air to become more and less dense
what is the wavelength equation?
wavelength = velocity / frequency
what is the standard/mean hearing threshold ?
10ˉ12 WMˉ2
what is the range of human hearing frequency and amplitude?
frequency - 20-20000Hz
Amplitude - 0-140dB
what can be defined through tuning curves ?
certain neurons have different frequency responsiveness
name the 3 parts of the ear
outer - ear drum
middle - ossicles
inner - cochlea
what does the ossicle bone do?
pushes against the oval windows
the bottom window allows flexibility
in what way does the middle ear act as a lever?
converts high amplitude force motion at ear drum into low force motion at the oval window
- vice versa
what is impedance matching ?
when bones match the impedance of the air into the fluid
creates small movement with high force
what is crucial for preventing hearing damage ?
stapedius reflex
explain the stapedius reflex ?
occurs during loud sound and speech
two muscle act on the ossicles
this causes the stapes to pull away from the oval window
which causes reduced transmission of vibrational energy to cochlea
what are the 3 chambers (scalae) of the cochlea - inner ear ?
inner - vestibuli
middle - media
outer - tympani
what separates the chambers of scalae?
and what does it do?
basilar membrane
movement of fluid causes the membrane to move
this activates the hair cells from movement in the tectorial membrane caused by basilar membrane movement
what is located between the scalae chambers, basilar membrane and reissners membrane ?
organ of corti
what do auditory hair cells detect?
physical movement through sound
what type of system is used to exaggerate sound in hair cells?
positive feedback
what is the role of outer hair cells ?
amplification
what causes hair cell inhibition?
stereocilia
what cause hair cell activation?
kinocilium
what is the pitch place theory ?
the helicotrema is a circular structure
- the further in the tighter the hole is
resonant frequency gets higher the further along
diff parts of basilar membrane is activated at diff frequencies
wider end - basilar membrane responds to high frequencies
tighter end - basilar membrane responds best to low frequency
what is used to see how much people can hear and how?
audiograms
sound activates areas like cochlea nerve and auditory cortex
explain wernicke’s area
located left temporal lobe
understanding speech
aphasia - speaking nonsense words
explain broca’s area
frontal lobe
producing speech
aphasia- can’t produce words/ speak
what is sound localisation?
distance and bearing and elevation of sound
what are key elements of sound that help judge distance ?
high frequency travel poorly
expectations
relative attenuation - gradual reduction in sound waves
echoes
what are key elements of sound that help judge direction?
inter-aural timing/phase differences
intramural volume differences
spectral colouring
what is inter-aural volume/time delays ?
head is a sound shadow so sound may reach one ear before the other
the delay can tell you the direction of where the person is depending on the size
how is the superior olive in the brain stem linked to hearing ?
each neuron travelling to the olive splits into 5 diff neurons
these are coincidence detectors
if hits 1+5 there’s a time difference
if hits 3+3 the sound is close by
what is a smaller sized head good at detecting ?
high frequency sounds
smaller time differences between both ears aids localisation
what is the cone of confusion?
sounds from opposite sides of the circle have same volume and time difference
sound from behind can sound infront
in animals what is high frequency calls for ?
avoiding localisation
no sharp onsets
in animals what is low frequency calls for ?
longer more intense and broad sounds attract attention
what is average auditory reaction time ?
140-160ms
