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73 Cards in this Set

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What is the natural resonance frequency of the EAC? middle ear? TM? ossicular chain?
EAC - 3000Hz
ME - 1000-2000Hz
TM - 800-1600Hz
ossicular chain - 500-2000Hz
What is the formula for determing the number of decibles?
dB SPL = 20log(po/pr)
where
po = pressure of the output of sound being measured
pr = pressure of the reference, usually 20 micropascals
What is the defn of 0 dB HL?
0 dB HL at any frequency is the least intensity needed for a normal ear to perceive a sound 50% of the time. 0 db HL is used as a reference and is a different dB SPL at different frequencies.
What is the defn of 0 dB SL?
0 dB SL is the level of intensity at which a particular individual can just perceive a sound 50% of the time. SL is a reference for an individual's threshold.
What is the volume of the middle ear?
1-2 cm3
At what frequencies do the tympanic membrane and ossicular chain most efficiently transmit sound?
500-3000Hz, the frequecies of speech
What is the ratio of the area of the vibrating portion of the TM to the area of the stapes footplate?
17:1 - vibrating portion of TM is 55mm2 and stapes footplate is 3.2mm2
What is the transformer ratio of the middle ear?
22:1 - the handle of the malleus is about 1.3 times longer than the long process of the incus, resulting in a lever ratio of 1.3. Multiplying the lever ratio by the area effect ratio - 17 x 1.3 = 22
Which hair cells (inner or outer) trigger the preponderance of afferent nerve responses?
Inner hair cells: 95% of all afferent fibers innervate the IHCs
What is the tonotopic organization of the cochlea? What frequencies are most sensitively detected at the basal end? the apical end?
basal - high freq
apical - low freq
What is the sequence of nuclei that a signal passes through from the cochlea to the auditory cortex?
E: eighth nerve
C: cochlear nucleus (at the pontomedullary junction)
O: superior olivary complex (in the lower pons)
L: lateral lemniscus (in the pons)
I: inferior colliculus (in the midbrain)
M: medial geniculate body (in the thalamus)
Where is the first point of decussation of the auditory signaling pathway?
at the superior olivary complex in the lower pons of the brainstem
How many fibers are in CN VIII?
~ 25,000
What is the maxiumum output of a tuning fork?
~ 60dB
A negative Rinne response implies a different degree of conductive hearing loss using different tuning forks. What do negative Rinne responses using the 256Hz, 512Hz, and 1024Hz forks imply?
256Hz - air-bone gap ≥ 15dB
512Hz - air-bone gap ≥ 25-30dB
1024Hz - air-bone gap ≥ 35dB
What is the Bing test? and what is a negative Bing test?
Eamines the occlusion effect. Tuning fork is placed on mastoid process while the tester alternatively opens and closes the ear canal with a finger.
Negative test means that the tone is not louder with the canal occluded and suggests a CHL.
What does the Schwabach test compare and what does it assume?
Compares the patient's bone conduction hearing to that of the examiner. Assumes that the examiner has nl hearing.
What does the Gelle test examine? How?
Assesses if TM and ossicular chain are intact and mobile. Tuning fork is placed on mastoid, then varying amounts of pressure are applied to the TM. Nl response should be decreased hearing with increase in pressure.
What is the defn of a hearing threshold?
the lowest levels at which a patient responds at least 50% of the time
When is it necessary to test interoctave frequencies?
for 25db or more difference between octave frequencies
What is the interaural attenuation for air conduction using supraaural earphones? insert or tube earphones?
40-65dB for supraaural earphones
80-90dB for insert earphones
What is the interaural attenuation for bone conduction?
0-10dB
When is masking required when testing air conduction?
Mask the non-test ear when the air conduction level of the test ear exceeds the bone conduction level of the non-test ear by 40dB or more
When is masking required when testing bone conduction?
Mask the non-test ear when the air-bone gap in the test ear is > 10dB
What is the speech reception threshold?
lowest level in dB at which a patient can repeat spondaic words (spondees) 50% of the time
What is a spondee?
a two-syllable compound word that is pronounced with equal stress on both syllables
How is the SRT used to confirm pure-tone thresholds?
SRT should be within 10dB of the pure-tone average
What are the frequencies used to calculate the pure-tone average?
500, 1000, and 2000 Hz
What is the speech awareness/detection threshold?
lowest level in dB at which an individual responds to the presence of speech
What is the speech recognition score?
percentage of phonetically balanced words that a patient repeats correctly
At what SL is the speech stimuli typically presented to determine the SRS?
30-40 dB SL
What is suggested by a type B tymp with nl ear canal volume?
with increased ear canal volume?
nl ear canal volume: fluid
high ear canal volume: perf
What is the volume of the EAC?
2cm3
What is suggested by a type C tymp?
ETD
What are three causes of type As tymp?
otosclerosis
malleus fixation
scarred TM
What are two causes of type Ad tymps?
ossicular dislocation
flaccid TM
At what dB HL will acoustic reflexes be elicited?
70-100db HL
Reflexes will be absent in what two circumstances?
1. conductive pathology
2. SNHL > 65dB HL
What are the descriptions of hearing loss for various thresholds?
10-20 dB - WNL
21-40 dB - mild
41-55 dB - moderate
56-70 dB - moderate to severe
71-90 dB - severe
>90 dB - profound
What is maximal CHL?
60 dB HL
What frequencies affected by pathologies that increase middle ear stiffness (eg. otosclerosis, fluid)?
low frequencies
What frequencies affected by pathologies that decrease middle ear stiffness?
flat loss
What frequencies affected by partial ossicular discontinuity?
high frequencies
What frequencies affected by pathologies that alter only mass of the middle ear?
high frequencies
What produces a loss in both low and high frequencies with a characteristic peak at 2000Hz?
Significant effusion - that affects both stiffness and mass.
What is "recruitment" and where is the lesion that it suggests?
Recruitment is abnormally rapid loudness growth in a poorer hearing ear and suggests a cochlear dysfunction rather than a retrocochlear problem.
What is the short increment sensitivity index? What is significance of a low score on a short increment sensitivity index?
1. Start with 1000Hz tone presented at 20dB SL.
2. Increase by 1dB increment 20x every few seconds.
3. Patient indicates when detects loudness "pips".
Low score suggests a nerve VIII lesion.
What is does Bekesy audiometry test?
auditory adaptation or fatigue
Describe the types and interpretation of Bekesy audiometry results.
type I: I and C tracings overlap, normal
type II: C drops 10-20dB below I above 1000Hz; suggests cochlear site (93% sensitive)
type III: C drops steadily below I, beginning in low frequencies, by as much as 50dB; suggests nerve VIII site (49% sensitive)
type IV: C drops below I, beginning in low frequencies, by about 30dB but courses parallel with I; suggests nerve VIII site
type v: C is above I; suggests nonorganic hearing loss
Describe the tone decay test.
1. continuous tone presented at or slightly above treshold
2. if perception of tone not maintained for 60 sec, add 5dB and begin anew
3. continue until patient maintains perception of tone for 1 min
What is suggested by decay beyond 25dB in a tone decay test?
nerve VIII lesion (sensitivity 70%)
What is "rollover"?
When SDS decrease at higher intensities. Slight rollover suggests cochlear lesion. Marked rollover suggests nerve VIII lesion.
What is normal performance on an acoustic reflex decay test?
maintenance of muscle contraction for 10 seconds at 10dB above acoustic reflex threshold
What is failure of an acoustic reflex decay test? What does it suggest?
Loss of half of the amplitude of the reflex in 5 seconds at 1000Hz and especially at 500Hz. Suggests retrocochlear lesion.
Describe the glycerol test for Meniere's Dz.
1. patient ingests 6 ounces of mixture of 50% glucose and water
2. PTA and SRS measured before and 3 hours after
When is the glycerol test considered positive for Meniere's Dz? (3)
1. 15dB improvement in threshold for at least one freq between 250 and 8000Hz
or
2. 12% improvement in SDS
or
3. SRT improves by > 10dB
What meds can affect ABRs? (3)
phenytoin
lidocaine
diazepam
Does coma or sleep affect ABRs?
no
What are spontaneous OAEs used for?
little clinical utility
What are the three types of evoked OAEs?
1. transient evoked - evoked by click
2. stimulus frequency - evoked by continuous pure tone
3. distortion product - evoked by two simultaneously presented pure tones
What is suggested by absent distortion product evoked OAEs with normal middle ear function?
At least a 40dB cochlear hearing loss.
What disease is suggested by SNHL, abnormal ABR, absent acoustic reflexes, poorer word-recognition ability than expected based on the pure-tone audiogram, but with present OAEs?
Auditory Neuropathy
Describe Stenger test.
Performed to detect malingering of unilateral loss. If sound is presented to both ears, patient will deny hearing in the ear with the feigned loss. If sound is presented to the good ear at a suprathreshold level, simultaneous to a louder sound in the questionable ear, a malingerer will localize the sound to his "bad" ear, and therefore deny hearing anything at all.
Describe the basis of the Lombard test.
Based on the phenomenom that one increases the volume of one's voice in the presence of loud background noise because the noise interferes with self-monitoring.
Describe the basis fo the delayed auditory feedback test.
Based on the principle that individuals monitor the loudness and rate of their speech by an auditory mechanism.
Which ear should be aided in cases of marked asymmetry?
the ear with hearing in the 40-70 dB range
Describe the classes of hearing aids? (4)
1. peak clipping
2. compression limiting
3. wide dynamic range compression
4. programmable
Describe a CROS hearing aid. What about a BiCROS?
CROS (contralateral routing of signal) for unilateral, unaidable hearing loss - a CROS aid picks up the signal on the poor side and routes it to the normal hearing ear to a nonoccluding ear mold.
BiCROS is when the better side still requires a hearing aid.
What degree of SNHL represents the limit of what is aidable with a BAHA?
45 dB
What history is suggested by a patient with an asymmetrical 4000Hz notch loss?
Using a gun. Hearing is worse in ear opposite the shoulder from which gun is fired.
How much sound attenuation can earmuffs or earplugs provide?
20-40dB of sound attenuation
What is the OSHA permissible noise exposure for 8 hours?
90 dB SPL
What is the relationship between permissible noise exposure time vs. SPL level?
For every 5dB SPL increase in sound, one must reduce the time of exposure to one half.