Unit 1 - Lecture 1 Flashcards
1
Q
What is conduction? What is modified?
A
How sound travels (the pathway and modification of amplitude, frequency, and timing)
2
Q
What is the normal pathway of conduction? What are some key points?
A
Air conduction (AC)
- Ear canal - Eardrum - ME bone chain - Inner Ear
* traveling wave -OC vibration
* hair bundle deflection (control transduction ion channel to generate receptor potential)
* OHC active force (loop back to IHCs - mech-electrical-mech-hyraulic)
3
Q
What is outer ear resonance due to? What does a standing wave do?
A
Standing wave (provides amplification by resonance - an object/system vibrates most easily at its natural frequency, response to an input signal)
4
Q
Equation for resonance
A
f =n* c /( 4 * L)
- L = 2.6 cm, the length of tube, sealed at one end
- c = 33,100 cm /sec, sound speed in air
- n= positive integer number
- f = 33,100/10.4 = 3186 Hz, when n=1
- Multiple resonances corresponding to n = 1, 2, 3…….
5
Q
What is a standing wave generated by? What happens to amplitude and vibration?
A
- the insert and rebound sound wave
- amplitude is doubles and vibration appears to be standing (node = 0 vibration)
6
Q
What is frequency response/transfer function?
A
how gain/phase changes with frequency
7
Q
What is gain? What does gain vary across?
A
output/input (in ration or dB)
dB gain = 20log (pressure ratio) 10log (intensity ration)
The gain varies across frequency range of hearing (frequency response, how the system modifies the signal in frequency)
8
Q
Explain the microphone gain picture
A
- Measurement for flange, sound pressure is compared between M2 and M1 (microphone)
- Larger contribution at canal for standing wave
- Flange effect is seen as the difference between M2 and M1 (M2-M1 = finding the gain of the flange)
9
Q
Resonance measured in the external ear (what is the number, what is the largest contribution from)?
A
15dB around 3000Hz (largest contribution from the meatus)
10
Q
What filter does the outer ear use?
A
bandpass filter
11
Q
Explain the different filters
A
- bandpass: low and high pass
- low pass: everything below 3dB is left untouched (only low frequencies pass)
- high pass: cut off point is 3dB lower than the starting point of the frequency, everything aboce that is left untouched (only high frequencies pass)
- band reject
12
Q
Age related changes with frequency response
A
we lose high frequency sounds as we age
13
Q
3 dB stands for ____
A
50% reduction of intensity
14
Q
What is the role of middle ears in land animals?
A
Impedance matching
15
Q
What are the 3 middle ear mechanisms that provide fain for compensating impedance match? What is the mismatch between?
A
- area action, gain = 25dB
- lever action, gain = 2.5dB
- buckling action, gain = 6dB
30dB attenuation due to impedance mismatch of air and water
16
Q
ME transfer function (freq, filter, shape)?
A
- bandpass
- peak around 1000Hz (1kHz)
- ME is broader (less of a peak, covers a wider range of frequency than OE transfer function)
17
Q
Where does ME transfer function decline?
A
declines towards high frequencies (and low)
18
Q
Why does the ME transfer function decline towards high frequency?
A
- Mass effect: experiment data by changing mass (increasing mass, reduce high frequency cutoff), makes high frequency sound more difficult to transfer
- less decline at high-frequency in more recent evaluations (suggesting error by equipment)
19
Q
Why is there decline at low frequency in ME transfer function?
A
due to elastic feature (stiffness) from: TM stiffness, ME ligament tense, air pressure in ME
20
Q
Explain the combination of external and middle ears
A
- ME frequency transfer function is broader, EE is narrower, put them together for a combination for a peak amplification around 3000 Hz and peak gain around 35 dB (EE 15 + ME 20)
- Most ME gain is around 20 dB
21
Q
What is efficiency?
A
- the ratio of power between eardrum and oval window
- what is the difference from perfect (100% compensation)?
- 10log.65 = -1.87dB
- If ME works perfectly well, the sound that goes into the IE should have no attenuation (this is considered as 100%), however the ME does not really provide perfect transfer conduction.
- The best efficiency is only 35% at peak (but only less than 2 dB).
22
Q
What proves that there is less decline in ME transfer function at the high frequencies?
A
- wider frequency range seen in later observations
- Hutten-Brink and Huddle (1994) and earlier studies showed lower cutoff at high frequency (calibration error?)
- See Puria et al (1997): suggesting much wider range (to high F) of ME response
- Attenuation towards high frequency is less (isn’t as big of a dip in the high frequency that we thought)
23
Q
How does an AC abnormality impact hearing?
A
- If there is a big eardrum perforation (occurs through repeated otitis media)
o external ear - ME air cavity (not through bone chain) - inner ear (through both oval window and round window)
o Hearing loss up to 30 dB (still some AC) - If air pathway is blocked, AC is not working at all, larger attenuation is expected (e.g., aural atresia – developmental deformation of temporal bone, EE does not open at all, no canal, sound can only be delivered to IE through bone conduction): 50-60 dB (when relying on natural BC alone, no AC)
24
Q
Bone conduction (natural vs. artificial)
A
The conduction of sound to the inner ear through the bone of the skull.
Natural BC (just sitting there, generally useless because there is such a huge air bone mismatch/impedance )
- Air to skull (air to solid)
- greater loss (50-60 dB) due to large impedance mismatch between air and bone
Artificial BC
- bone vibrator (placed onto the mastoid surface so vibration goes through skull to IE)
- Skull
- inner ear
25
Why do we study BC?
- For diagnosis:
To differentiate between conductive HL and sensorineural HL
- For amplification in rehab:
BC hearing aids are used for various reasons, especially when AC aids do not work appropriately
- For Research:
To understand the function of the IE
26
If AC doesn't work there is ___ hearing loss
conductive
27
If BC doesn't work there is ___ hearing loss
sensorineural
28
What are some BC products?
- Ear-free headphones
- Hearing aids and assistive listening devices
- Specialized communication products (for underwater and noisy environments)
29
When is a bone vibrator (bonephone) used? What happens to the current?
Used in clinical tests (placed against skull and an electrical signal is transduced to convert electrical signal into mechanical vibration)
30
What is a bone anchored hearing aid (BAHA)?
Place directly in temporal bone and device is attached to deliver signal
31
What are some advantages & disadvantages of BC when compared to AC?
Advantages
- Ear free (EE Is not occupied)
- High sound clarity (?) in noisy environments - Need to be clear as compared between what (For people with severe hearing loss can regain hearing through bone conduction)
Disadvantages
- Sound level limit: less gain as compared with AC aids (air conduction provides more power)
- Reduced frequency bandwidth (bias to low frequency - works best at low frequency)
32
Limited evidence for ____ between AC and BC in quiet & noise
speech perception difference
33
What are some device and application problems for BC?
- the feature of vibrator,
- binaural interaction (BC goes to both ears),
- masking issue (masking should not go BC)
34
Differences between AC and BC
- Different pathways
- Efficacy
o In general, AC is better for both normal and artificial ones
o However, when AC pathway has problem, BC is better
- Resonance or transfer function:
o different from AC pathway
o Varies with conductive pathologies
35
Similarities between AC and BC
- Target of BC is the same as AC: cochlear hair cells (evidence below)
o AC vs BC cancellation (inverse phase) (Bekesy and Lowy), apply a tone of same frequency through AC and BC but opposite phase (for there to be a cancellation the sound much be reaching the same target for BC and AC)
- cochlear mechanics is almost the same for AC and BC
36
Model pathways for BC and AC hearing
Bone conduction: skin, skull bone, CSF
Air conduction: OE, ME, II
37
How does BC combine with AC?
BC overlaps AC, sound conducted by bone can get to AC pathway
BC is not purely BC, it is partially overlapped through multiple pathways with AC (this is the reason why conductive pathology can impact the result of BC)
38
BC Mechanisms (pathways)
BC by AC (via ME)
1. Osseotympanic BC (skull bone, EE, TM)
2. ME Inertial BC (skull, initial force of ME)
BC (bypass AC)
3. Compression/Distortion BC
4. Fluid Inertia in cochlea (skull, IE through forces)
5. CSF (inertia, compression)
39
BC Mechanisms - 1. Osseotympanic Bone Conduction
- vibration of skull including the walls of ear canal and ME (radiation into ear canal and ME)
- then sound conducts through AC from ear canal
*vibration (two directions = leaking) also leak out (related to occlusion effect)
- frequency: more important at low-f
*evidence: AC/BC cancellation in external ear canal for fre < 0.7kHz
- overall importance isn't huge
- occlusion effect: when external ear canal is blocked, this component becomes more important
40
Closed vs. open ear drum
- BC is less efficient when the ear canal is open
- Much less stimulation is needed when the ear canal is blocked
- Need to apply lower sound level to reach the same vibration when the ear canal is blocked (if you don’t change the sound level, you will see that sound is louder when the ear canal is blocked)
41
What is the occlusion effect? What frequency?
- increase of SPL to inner ear when ear canal is closed, resulting in decreased threshold in BC
- occurs in frequency below 1 kHz (because BC favours low frequency)
- sound. into OE/ME via osseotympanic mechanism can go both ways, into cochlea and leaking out
- mechanism: energy leaking is blocked in the occlusion effect so it can only go into the cochlea and there is an increase in sound pressure in the inner ear
- if you don't change the sound level, more sound will get into the inner ear
42
The occlusion effect increases ____ in ear canal: low-f.
Explain this...
SPL
- The reference is 1 pascal (94 dB SPL) per Newton.
- Exact SPL produced by 1 N varies with Fre. and occlusion
- Larger negative values mean lower SPL
43
Explain 1 pascal/Newton
- 1 pascal produces 94 dB SPL in air
- Newton is the unit of force
- 0dB is the reference that one N produces 1 pascal of sound in the ear canal
44
Detecting the occlusion effect by the bing test tuning fork test
- Proposed by a german otologist albert bing
- Tuning fork testing was used to distinguish between CHL and SNHL
- vibrating low-f tuning fork on mastoid
- normal or SNHL subjects heard sound louder when ear canal close (bing test positive)
- bing test negative: no difference between closed and open ear canal, conductive HL
45
What is the OE impact on the standard of BC test?
- Must leave the ear canal open to avoid occlusion effect
46
BC Mechanisms - 2. ME bone-chain inertial effect
- Ossicles-ligaments: a spring-mass system
*Spring = ligaments, mass = ossicles
- Inertial effect: the mass of the ossicle chain
- Evidence: increased TM mass enhances BC sensitivity, increased stiffness decreases BC
- Frequency region: low frequency (<2kHz, or around resonant Fre: 1-3 kHz)
- Confusion in discussion of frequency:
*At low freq., springs move ossicles in phase with skull
*At high fre., inertial force overcomes spring’s stiffness, resulting a relative motion of stapes
47
What is the impact of stiffness and mass on frequency response?
- Increasing stiffness attenuates low frequency
- Increasing mass attenuates high frequency
48
lateral placement of vibrator (mastoid) vs. frontal placement of vibrator (forehead). What is the difference?
- Vibrator on the forehead has less inertial effect (directly perpendicular to the bone chain)
- Difference of < 10dB between the two
- Vibrator on the mastoid fully utilizes the inertial effect (bones had the tendency to move in that direction)
49
Removal of the ossicles impacts ___ slightly
BC
- this mechanism is not significant, but can cause variation in subjects
- removing the ossicles the threshold would increase
- not significant in normal subjects
50
BC Mechanisms - 3. Compression bone conduction
- depends on
- what frequency
Depends on:
- Volume difference between scala vestibuli and scala tympani
- Flexibility difference between oval window and round window
- Vestibule space and endolymphatic sac through cochlear aqueduct
- Fre: <=4kHz
- Significance: not important
51
Distortion of bone conduction (compression & what happens to the BM)
- compressed vertically: BM moves up
- compressed horizontally: BM moves down
- shape change causes the bending of the BM, eventually stimulating the hair cells
52
BC Mechanisms - 4. Inertial of cochlea fluids
- inertial force of cochlea fluids can cause fluid movement when allowed
- the allowance is established by two windows, driving force is pressure gradient between them
- significance: the most important contributor
53
BC Mechanisms - 5. Through CSF
- pathway: cochlear aqueduct
- fact: obstruction of aqueduct affects BC
- significance: need more studies, unlikely to be an important one
54
Airborne sound in BC is ___dB less sensitive than the AC for normal hearing subjects
40-60
55
Fluid inertia mech is ___dB greater than compression mech in normal ear
20
56
Otosclerosis of stapes depresses ___.
fluid inertia
57
Practical issue 1: occlusion effect
- definition
- when does it occur
- how will threshold change
- what frequency
- what can we do about it
- Definition: sound through BC becomes louder when external ear is blocked. Threshold also decreases
- When does it occurs? When using earphone – remove earphone for BC test
- How will thresholds change? Better than it should be
- What frequency? Low frequency
- What can we do about it? Leave the canal open when doing BC test.
58
What are the 3 tuning fork tests?
1. bing test
2. weber's test
3. rinne test
59
What is the bing test?
- on mastoid
- comparison between outer ear closed and open (no difference in CHL)
60
What is weber's test?
- 256 Hz on forehead
- defective ear hears better = CHL (occlusion effect naturally occurs)
- normal ear hears better = SNHL
- subject supposed to have asymmetrical HL
61
What is the rinne test?
- 512 Hz first on mastoid (BC) then outside the ear (AC)
- normal AC > BC
- need to move quickly
- typically together with weber's test
62
Practical issue 2: impact of conductive loss on BC (Middle ear problems)
- bone chain fixation
- bone chain disconnection
- filled wth fluid
- what are the results?
1. bone chain fixation (loss of 1. osseotympanic BC and 2. ME inertial BC)
- can be caused by otosclerosis and otitis media
2. bone chain disconnection (mech 2. ME inertial BC can be stronger or weaker depending on the location od disconnection, loss of mech 1. osseotympanic BC)
3. filled with fluid (stiff ME, increased mass load loss of mech 4. fluid inertia in cochlea)
4. typical result: carhart notch (2000 Hz - BC vs AC threshold difference)
63
Explain carhart notch
- increased BC threshold at 2k, in AC pathology, A case of Otosclerosis
- Lower threshold for AC = Carhartt notch
- difference between AC and BC thresholds is the air-bone gap
- Carhartt notch = narrowest air-bone gap
64
What does the carhart notch tell us?
- smallest air-bone gap at 2kHz
- AC pathology impacts BC threshold
- not entirely sure why it occurs at 2kHz (due to the loss of the middle ear component close to the resonance point of the ossicular chain)
65
Carhart Notch - a case of malleus fixation
- The Carhart notch is “masked” by the mixture of SNHL at high frequency. The “preop BC (frontal)” shows less impact by the fixation.
- Mixed HL
66
Carhart Notch - a case of OM
- Carhart notch is not specific to Otosclerosis
- Hearing recovered; air-bone gap disappeared
67
Vibrator placement and age (theoretically and reality)
Theoretically, no attenuation with distance and therefore no location effect if
- skull is fused as one bone
- skull is purely bone (no soft tissue)
- BC is pure “BC”.
Reality:
- ME Inertia effect change with place
- Soft tissue varies with thickness around skull
- Force change with location
- Therefore, best place for vibrator is the mastoid
Age and skull development impacts BC
68
Age effect on BC
Place (bigger location effect is seen in young children: mastoid is better than forehead because the tissue is still soft when will attenuate sound)
Tissue (soft tissue between bones buffers vibration)
Change (small head will change the force applied to the vibrator)
69
Masking in BC
- purpose is to mask untested ear (vibration fro bone vibrator will go to both ears equally, therefore need to mask)
- Intensity 50 dB HL is safe and adequate in most case
- Masker must be delivered through AC (cannot mask through BC or it will mask both ears).
- Conductive HL and masking dilema (how to deal with - Insert earphone for masking (improves masking by using less power; less leaking).
70
What is acoustic reflex? narrow definition
- ME function that is controlled by our nerve system
- acoustic middle ear reflex
71
What are the middle ear muscles?
Stapedius Muscle
- Smaller one, but more effective
- Attached to stapes
- Pull tympanic membrane and stapedius laterally
- Footplate of oval window is more fixed posteriorly (swings like a door)
- May be the only one involved in AR in human
Tensor Tympani
- Attached to manubrium
- Larger
- Pull TM medially
- Tensor tympani contraction pulls the eardrum inward
72
ME muscles and AR
- what is the input
- what is the output
- what is the effect
- loud sound evokes AR
- the output is the contraction of ME muscles
- the effect is increased stiffness (low-f is attenuated more)
- In humans, stapedius muscle plays a greater role in AR
73
Evidence supporting stapedius
- observation in normal ear
- observation in pathalogical ear
Observation in normal ear
- Eardrum movement during AR
- Recording of muscular potential during AR
- Measure air pressure change during AR
Observation in pathological ear
- Bell's palsy (one side of facial nerve is paralyzed disappearing AR, TMM is still there, but not SM, indicating SM is the most important for AR)
- selective fixation or damage to certain muscle (or paralyzing)
74
Neural circuits for AR
- Sound to one ear will cause AR In both ears (SOC sends it to both sides)
- However, short circuits are unilateral (SOC --> facial motor nucleus Innervation to the SOC is bilateral (other sources say that the pathway from SOC --> FNN is contralateral)
75
What is the short way for AR? What is the long way?
short: CN --> FNN
long: CN --> SOC --> FNN
76
What are the basic features of AR?
- level for pure tone and noise
- where are the delays
- Evoked by loud sound (>=80 dB pure tone; >=65 dB noise, SPL)
- Delay in neural circuit as well as Muscles (time delay is larger)
- Binaural response to unilateral stimulation
- When vocalizing, muscle contracts in advance (50-70 ms in chicken)
- Contraction of ME muscles can also be evoked by irritation of face, ear canal, etc (stronger for tensor tympani muscle)
77
What two ways can AR be measured?
Direct Measurement
- Electromyogram
- Direct observation through perforated TM
Indirect Measurement
- Measure deflection of eardrum (deflection of light by ear drum movement)
- Measure air pressure in sealed ear canal
- Measurement of ME impedance: AR changes ME impedance. This is an important diagnosis tool.
* Done in ear canal as the ear drum is acoustically transparent
78
Carhartt notch is mostly associated with ____.
otosclerosis
79
Masking dilemma happens to patients with ____ hearing loss
AC
80
Mass ____ with frequency and stiffness ____ with frequency
increases, decreases
81
Admittance vs. impedance
Admittance tells us how easy sound can be conducted
Impedance is the opposition to flow
82
Conductance vs. Resistance
Resistance tells us how difficultly sound can be conducted
Conductance is the opposite of resistance (how easily a sound can be conducted)
83
Susceptance vs. reactance
Reactance is how much it reacts to change over time
Susceptance is how much it could change
84
Admittance is inversely related to ____ when the system only contains resistance (no other components)
When it is only reactance, the the impedance is equal to the ____
impedance
susceptance
85
smaller the volume, larger the ____
impedance
86
Stiffer the TM the more ____
impedance
87
Impedance bridge
Would use an impedance bridge to match the volumes in the ear
88
Equivalent Volume (Ve)
- The volume in solid cell that matches the impedance of in ear canal
- Equivalent volume = volume surrounded by solid wall (in the ear canal one end is surrounded by soft tissue)
89
Standard condition of Ve
- Standard air pressure at sea level
- Defined temperature
- Cell with solid wall
90
Z is proportional to 1/Ve in ____
low frequency
91
Comparison between Ve and real ear V (external ear behind plug)
- Real ear: surrounded by soft tissue and eardrum.
- A cell with solid wall have larger impedance as compared with a cell of the same size but with soft wall.
- To make them equal in impedance, Ve must be larger than V. Therefore, Ve is larger than the real V in ear canal.
- As volume goes up, impedance goes down
- Real V has soft end and therefore smaller impedance as compared with the cell of the same size but surrounded by solid wall. Therefore, a solid cell must have a larger volume to have equal impedance as that of the real ear. There for Ve is larger than V in real ear.
92
Explain the ear drum being acoustically transparent
- OE and ME should have the same impedance, can measure the impedance of the ME through the OE.
93
What does ME impedance change?
- Middle ear impedance change will change the stiffness of eardrum
- Therefore, change the Ve
94
If stiffness is increased when AR is activated, Ve will?
go down/be smaller
95
What will happen in Ve if ME is full of water?
Ve smaller because the water cannot be compressed (impedance is large)
96
What will happen if there is a large perforation on eardrum?
Ve largely increased
97
What will happen if the bone chain is disconnected?
Ve will be increased because the TM is more flexible
98
Why do we use Ve?
The variable size of the canal is unknown
99
What are the 2 sounds used in AR measurement?
1) continuous tone (low f) for impedance measuring (below AR threshold)
2) loud sound for impedance change (could be low and high in frequency)
100
Why change air pressure in AR measurement?
- Changing air pressure allows detecting of middle ear pressure.
- How? The OE pressure that results in the smallest impedance is the pressure of ME – the TM is most efficient when the pressure is equal on both sides
101
Middle ear elements to admittance
Mass
* Pars flaccida of TM
* Ossicle chain
* Perilymph in the cochlea
* When ET open
Stiffness
* Ligaments
* Muscle tendons
* TM
* Air enclosed in ear canal (during test and ME
Resistance
* Bone joints and cochlear mechanical structure
102
High impedance = low ____
admittance
103
Stimulus parameters for AR
- signal spectrum
- duration
- signal presentation
Signal spectrum
- middle fre is better
- noise is better than puretone
Duration
- >200 ms for temporal summation (adaption)
Signal presentation
- bilateral > ipsilateral > contralateral
- However, contralateral AR is often requested due to the ability to exam the whole circuit for AR (in clinic)
104
Explain testing two tones by frequency and what happens with AR and CB
- When the separation is in CB, no change in AR threshold
- When the separation is over CB, threshold drops down. Turning point tells CB.
- AR threshold gets lower as CB gets wider
105
What is cross band summation?
Apply signal across more than one critical band, broadband signal, the more CB involved, the lower the threshold
106
Intensity Effect
- how does it appear
- AR magnitude (how strong AR is) increases with intensity above threshold
* Can be easily saturated and its limit is 20dB
- Appears as:
* Increase in impedance
* Decrease in latency
107
How to define threshold
Threshold: 0.03 cm3 or 10% of individual maximal (10% is less used as we don’t always know the maximal as that can be damaging)
108
Latency
- length
- relation to intensity
- 2 sources
- Latency change with intensity from 150 ms (longest) to 25-30 ms (shortest)
- Higher the intensity shorter the latency
- Latency comes from two sources: neural circuit delay (signal goes past several synapse, the less important factor) and the delay in the response of middle ear muscle (more important factor).
- Which one is larger (longer)? Muscular delay (muscles are slower than the neural stuff).
109
Physiological meaning of latency
AR functionally is supposed to provide protection of ME against loud sounds, however, this protection is very limited to the pulse signal (gunshot), pulse signal (no protection), multiple (protection)
110
AR Threshold
- Decrease with signal duration: larger time range for the temporal summation (up to 500 ms = 0.5 s)
- It is easier for AR to occur when the stimulus is played for a longer time
- Longer duration there is a lower threshold
111
Where is there more summation in AR?
High frequency
112
AR adaptation
- when does AR drop off faster
- Reduction of AR during long lasting stimulation
- AR drops off faster with higher frequency
113
Reflex decay abnormal
- >50% in 5 sec
- Retrocochlear pathology (past cochlea)
- Bell’s palsy
114
AR on middle ear conduction (overall, what happens)
- An increase in stiffness increases impedance (loudness goes down)
- Therefore, attenuation at low frequency
115
A system with higher stiffness has high ____ because it does not respond well to low F signal
Natural frequency
116
Explain the steps of AR
1. Loud sound initiates AR
2. AR reduces low frequency sound into cochlea
3. Therefore, AR is reduced
4. Then more sound gets into cochlea - AR increases again
5. Repeat 1-4: osscilation
117
AR in unilateral Bell palsy
- If you measure the paralyzed ear, you will not get AR, therefore test in healthy ear
- Stimulating the contralateral ear for Bell’s palsy is more effective
- Plateau in growth function with Bell’s palsy
- Paralyzed ear receives a stronger input (less sound attenuation from the muscle contraction) as the intensity level of the stimulation increases
- Sound in paralyzed ear, normal ear will overcompensate for AR (ctrl)
- Sound in normal ear, AR will be normal (ipsi)
118
Temporal threshold shift
- TTS (temporal threshold shift – hearing loss caused by noise)
- Go to concert and next day ears are ringing
- Induced by low frequency noise
119
Increased stiffness attenuates sound transmission at ______
- Increased stiffness attenuates sound transmission at low frequencies (< 1000 Hz).
- This is thought to provide some protection against noise exposure.
120
ME muscle contraction evoked by others
Swallowing, yawning, tickling on face, etc
vocalization
121
Intensity-control theory:
- Reduces high level sound. Therefore, provides protection
- Currently, this protection against noise is not considered as the main role of AR
122
Perceptual Theory:
Improve hearing by:
- Protection from intense noise
- Reducing low-f masking
- Distinguish between own vocalization and external signal
- Prevent roll-over
* Increasing the stimulus intensity but are getting a decrease
* Decrease in discrimination score (% correct) at very high levels
* Making it louder but it doesn’t sound louder
* Limit to AR
- Thoughts on what AR does (more accepted)
123
People with Bell’s Palsy have increased ____ because they don’t have an AR
roll-over
124
Potential sources of artifacts
artifacts = huge variation between individuals on same test
- Previous ME diseases
- Sequential variability
- Test operation
- Age
- Medications
125
CF is defined by the frequency with the lowest ____.
- At low level, ____ = ____
- At high level ____ < ____
Threshold
-At low level, BF = CF
-At high level, BF < CF
126
When we record at 10k region in response to 5k tone, only ____ can be seen
passive component
127
Evidence From Behavioural Study
- Low level probe tells peak vibration on BM
- High probe will spread to other places and we don't want that
- Low level probe tone for accurate reading, need delay between masker & probe tone
128
Receptor Potential in Response to Sinusoid Stimulation (what does it contain, what do each do, what are the frequency)
- Contains DC and AC current
- AC component follows/copies stimuli (low frequency)
- DC component shifts from baseline (high frequency)
