Audition

Question 1

complex vibrations

Answer 1

resolved into sum of individual sinosoidal vibrations

Question 2

sine waves characterised by

Answer 2

frequency, amplitude, phase

Question 3

changes in amplitude

Answer 3

changes in loudness

Question 4

changes in frequency

Answer 4

changes in pitch

Question 5

range of intensities heard by the ear

Answer 5

10 ^12

Question 6

reference value for human psychoaccustics

Answer 6

20 micro Pascal

Question 7

decibel

Answer 7

unit of power in auditory reserach

one tenth of a Bel

is a ratio - strength of signal in relation to reference value

Question 8

threshold of human hearing

Answer 8

3kHz

Question 9

dB SPL

Answer 9

decibel sound pressure Level
signals expressed relative to threshold of human hearing

can’t express zero sound in dB

Question 10

doubling of pressure =

Answer 10

increase in level of 6 dB

Question 11

doubling of power =

Answer 11

increase in 3 dB

Question 12

low-pass filter

Answer 12

filter that passes only frequencies below a designated ‘corner’, or cut-off frequency, while attenuating higher frequencies

Question 13

high pass filter

Answer 13

filter attenuates frequencies below the corner frequency.

Question 14

band pass filter

Answer 14

passes frequencies within a restricted range or bandwidth.

The corner frequency (fc) is the frequency at which the power output of the filter has dropped to 50% of its maximum i.e. the half-power point. ( decreese of 3 dB of relative output )

Question 15

animals individual differences

Answer 15

wide variation in range of frequencies which animals can detect sound

eg whales dolphins wide range

frogs birds crickets small range

–> due to length of cochlea

Question 16

peripheral auditors system

Answer 16

the ear and the auditory nerve

Question 17

central auditory system

Answer 17

nuclei and pathways from the cochlear nucleus to the auditory cortex

Question 18

ear three parts

Answer 18

(a) Outer - pinna and external auditory meatus
(b) Middle - tympanic membrane, ossicles and middle ear cavity
(c) Inner - cochlea (includes vestibular
apparatus)

Question 19

external auditory meatus EAM

Answer 19

ear canal

open ended tube
resonant peaks due to length

gain ( dB ) coincides to frequencies important for human speech

Question 20

pinna

Answer 20

sound localisation –> modifies spectra of sounds in space-dependant matter

HRTF –> cue for sound localisation

Question 21

head related transfer function ( HRTF )

Answer 21

transfer function, from free field to the tympanic membrane

containing direction depended peaks and notches above 5 kHz –> cue for sound localisation esp for elevation

Question 22

sound localising is

Answer 22

plastic
humans can reinterpret the relationship between cues provided by HRTFs and direction in space ( i.e localise the elevation of sound ) when the shape of the pinna is changed within a couple of weeks

multiple representations of pf auditory space can coexist – probably due to neural growth of novel connections

Question 23

function of middle ear

Answer 23

impedance matching between air and cochlear fluids

protection from loud sounds including own vocalisations

anti-masking of high frequency sounds by low frequency sounds - particular at high sound levels

Question 24

middle ear muscles function

Answer 24

MEM –> dampen the vibrations of the ossicles –> reduce acoustic signal reaching ears

Question 25

properties of middle ear muscles

Answer 25

smallest skeletal muscles in the human body They contract about 100 ms after exposure to a loud sound and also before a person vocalises They are absent in frogs that do not vocalise They attenuate low frequencies more than high The MEM reflex is activated by sounds 80 - 90 dB above a person’s hearing threshold

Question 26

tensor tympani muscle connected to

Answer 26

neck of the malleus

Question 27

stapedius connected to

Answer 27

neck of the stapes

Question 28

stapedius active when ( humans )

Answer 28

exposed to loud sounds

Question 29

stapedius role

Answer 29

birds: reduce intensity of the sound produced when bird cries humans: improve hearing level of a person in noisy environment

Question 30

conductive loss

Answer 30

low frequency hearing loss of 30 dB or more

Question 31

sensorineural hearing loss

Answer 31

hearing loss through cochlea or auditory pathway damaged

Question 32

Rinne test

Answer 32

used to distinguish between conductive or sensorineural hearing loss places a vibrating tuning fork alternately on the mastoid process and at the entrance of the EAM conductive: - bone conduction, (transmission of sound to the cochlea via the skull) is unimpaired - response to sound conducted by the EAM is reduce sensorineural greater sensitivity to air conduction at the EAM in comparison with bone conduction.

Question 33

cochlea

Answer 33

decompose the acoustic signal into its component frequencies.

Question 34

frequencies mapped out

Answer 34

tonotopically along the cochlea with its length with equal increments in distance corresponding to equal increments in logarithmic frequency (i.e. the mapping is non-linear

Question 35

inner hair cells

Answer 35

contains ~3000 hair cells along the cochlear partition synapse with type 1 fibres

Question 36

outer hair cells

Answer 36

three rows totalling ~11000. | synapse with type two fibres ( unmylenated )

Question 37

basilar membrane vibration

Answer 37

Each point on the basilar membrane undergoes a sinusoidal vibration at the driving frequency. * The maximum amplitude of vibration corresponds to the characteristic place on the cochlea’s frequency map. * The pattern of vibration is not dependent on which end of the cochlea is stimulated

Question 38

cochlea function dependent on

Answer 38

active, mechanical feedback system | --> outer hair cells as agents thereof

Question 39

evidence for active feedback system

Answer 39

``` • Many aspects of cochlear function are physiologically vulnerable (Fig.15) • The ear can emit sound - otoacoustic emissions • Interruption of the OHCs alters the IHC response (see Fig. 16 below) • Passive models of the cochlea struggle to replicate the functioning cochlea. ```

Question 40

outer hair cells shape changes

Answer 40

depolarisation: length decreases hyperpolarisation: length increases

Question 41

inner hair cells

Answer 41

transduce mechanical events in the cochlea to electrical events in auditory nerve fibres

Question 42

outer hair cells function

Answer 42

actively assist mechanics of the cochlea responsible for, among other things, sensitivity, sharpness of tuning, emissions and the dynamic range amplify

Question 43

cochlea function

Answer 43

motor processes : with OHC transduction as an active process , negative damping of the mechanical properties of the organ and sensory processes: IHC transduction --> synaptic processes

Question 44

tip links

Answer 44

responsible for mechanical gating of the stereocilia - connect to it stretching ( due to displacing bundle of stereocilia ( hairs ) towards largest stereo cilia) --> probability of mechanically gates channels opening increases --> excitatory shortening -->probability of closing increases --> inhibitory

Question 45

movement in outer hair cells

Answer 45

due to relative movement between the reticular laminar and the tectorial membrane

Question 46

movement of inner hair cells

Answer 46

flow of endolymph fluid over the cilia

Question 47

transducer current in cilia

Answer 47

carried by K+ ions --> electrical driving force

Question 48

endolymph predominant cation

Answer 48

K+

Question 49

hair cell intracellular composition

Answer 49

few metabolic demands --> active transport rather needed for composition of the endolymph

Question 50

stria vascularis

Answer 50

controls composition of the endolymphatic fluid

Question 51

transduction in hair cells

Answer 51

place: tips of stereo cilia time: extremely fast

Question 52

evidence tip links role in transduction

Answer 52

observation that the largest current changes occur near the tips of the stereocilia rather than at their base

Question 53

otoacoustic emissions OAEs

Answer 53

sounds that can be measured in the external auditory meatus - -> evidence for active process - vibrations produced in the cochlea emissions: - evoked spontaneously - evoked by sound

Question 54

vulnerability of OAEs

Answer 54

evidence for OHCs are the mechanical effectors in the production of emissions

Question 55

Distortion product- evoked otoacoustic emissions (DPOAEs)

Answer 55

generated with the presentation of two tones (aka the primaries, f1 and f2) and the largest of these emissions occurs at the frequency 2f1-f2. sensorineural hearing loss lack OAEs used for neonates to establish absence of hearing

Question 56

inner hair cells - overview

Answer 56

``` sensory stereocilia fluid coupled passive detector of BM motion very robust strong afferent innervation weak efferent innervation hearing level > 60 dB SPL malfunction can cause total deafness ```

Question 57

outer hair cells - overview

Answer 57

sensori-motor stereocilia directly coupled to TM active positive feedback very delicate weak afferent innervation strong efferent innervation hearing level 0 - 60 dB SPL malfunction causes up to 60 dB HL

Question 58

electrical tuning

Answer 58

found in lower vertebrate not mammals depolarisation --> opening of calcium channels --> depolarisation calcium influx --> increase in potassium conductance --> depolarisation towards Ek frequency of oscillation according to position on basilar membrane

Question 59

lower vertebrates characertistic frequency due to

Answer 59

density and kinetic properties of calcium activated potassium channels

Question 60

output of cochlea

Answer 60

set of parallel, overlapping, bandpass filters

Question 61

characterisation of bandpass filters

Answer 61

quality of Q factor Q10 dB = CF/bandwidth 10 dB above CF threshold.

Question 62

characteristic frequency ( CF )

Answer 62

most sensitive point of the filter

Question 63

tonotopicity

Answer 63

preserved throughout auditory pathway from cochlea to cortex

Question 64

frequency resolution

Answer 64

the ability to detect one frequency component of a multi- frequency complex stimulus, when all components are presented simultaneously

Question 65

frequency resolution determined at

Answer 65

determined at level of basilar membrane overlap of psychophysical bandwidths and neural bandwidths

Question 66

frequency discrimination

Answer 66

ability to distinguish between two tones presented sequential

Question 67

phase locking

Answer 67

neurons only fire at a preferred phase in the cycle in low frequency auditory neurons --> construction of frequency representation of stimulus from phase- locked discharge --> use of temporal information still matter of debate

Question 68

upper limit of spike discharge

Answer 68

set by refractory period 100 Hz

Question 69

Auditory-nerve fibres division

Answer 69

three groups based on their spontaneous discharge rate Fibres with the lowest thresholds (the most sensitive)--> highest spontaneous rates highest thresholds (least sensitive) --> lowest SRs intermediate thresholds --> intermediate SRs

Question 70

spontaneous discharge rate SR

Answer 70

discharge rate of an auditory neuron in the absence of controlled acoustic stimulation

Question 71

auditory nerve fibres threshold determines

Answer 71

dynamic range low threshold --> narrow dynamic range the higher the wider

Question 72

ability to distinguish small intensity differences over wide range of sound levels due to

Answer 72

information of different fibres groups with varying dynamic ranges increase in the number of active fibres at high sound levels

Question 73

olivocochlear efferent system

Answer 73

descending fibres from superior olive to the cochlea medial and lateral systems brain able to influence output of both sets of receptor cells

Question 74

lateral system olivocochlear efferent system

Answer 74

cell bodies in or around the lateral superior olive (depending on the species) terminates on dendrites of the auditory nerve fibres role: unknown

Question 75

medial system olivocochlear efferent system

Answer 75

medial system has its cell bodies medial to the lateral superior olive, in the periolivary region of the superior olive. terminates on outer hair cells three main hypotheses concerning the role : - protection from loud sounds, - improving detection of sounds in noise, - controlling cochlear mechanics.

Question 76

temporary threshold shift

Answer 76

threshold increased following exposure of loud tone | recovery: h to days

Question 77

protection from increase in threshold

Answer 77

if exposure + electrical stimulation of medial olivocochlear system exposure to a loud stimulus in one ear is accompanied by an acoustic stimulus in the other ear ( n.b only if medial olivocochlear system uninterrupted )