2: Audiology Flashcards
What produces sound?
Energy waves of particle displacement, both by compression (more dense) and rarefaction (less dense) within an elastic medium
What is the definition of amplitude in sound?
The maximum displacement of a vibrating particle of the medium from its mean position
What is the definition of intensity of a sound?
The amount of sound energy through an area per time, refers to sound strength or magnitude
What is the definition of sound pressure?
Sound force (related to acceleration) over a surface per unit time
What is the definition of sound frequency?
Number of cycles (complete oscillations) of a vibrating area per unit time, correlates with pitch
What range of frequencies is the human ear able to hear?
20Hz to 20,000 Hz
What is a single frequency sound called (rarely occurs in nature)
Pure tone
What is the name for aperiodic complex sound?
Noise
What is the term for the frequency at which a mass vibrates with the least amount of force?
What determines it?
Resonant frequency
Elasticity, mass, and the frictional characteristics of the medium
What is a decibel
logarithmic expression of the ratio of two intensities
What is sound pressure level (SPL) a measurement of?
Sound strength
What does zero dL HL represent
Average lowest intensity perceived by normal hears 50% of the time
**HL=hearing level
What does zero dB SL represent
Level of intensity at which an individual can just perceive a sound in 50% of presentations (threshold)
What are the components of the external ear?
Auricle
EAC
Outer portion of the TM
What is the average resonant frequency of the EAC?
2700 Hz
What determines the displacement of the ossicular chain?
Frequency and the intensity of the sound
At what range of frequencies does the TM and the ossicular chain most efficiently transmit sound?
500-3000 Hz (normal speech)
What are the four factors that allow for impedance matching in the middle ear?
Surface area of the TM vs that of the stapes
Lever action of the ossicular chain
Natural resonance and efficiency of the outer and middle ears
Phase difference between the oval and round windows
What is the difference between the SA of the TM vs that of the stapes footplate?
TM: 85-90 mm2, only 55mm2 vibrates
Stapes footplate: 3.2mm2
17:1 increase in energy by concentrating the area
How much longer is the handle of the malleus compared to the long process of the incus?
1.3
What is the transformer ratio of the middle ear? What is it composed of?
22:1 (17 from the SA differential and 1.3 from the lever action)
Translates to 25 dB
What forms of energy is sounds changed between between the middle ear and inner ear?
Mechanical -> Hydraulic -> Bioelectric
The shearing motion of what two membranes causes bending of the hair cell stereocilia
Basilar
Tectorial
What fluid filled space in the cochlea is superior? Middle? Inferior?
Scala vestibuli
Scala media
Scala tympani
What membrane is found between the scala vestibuli and the scala media?
Reissner’s membrane
95% of the afferent fibers from CN VIII go to which hair cells?
Inner hair cells
What serves to adjust the basilar membrane’s physical properties so that a given frequency maximally stimulates a narrow group of inner hair cells?
Outer hair cells (have efferent innervation)
**serve as cochlear amplifier
Which frequencies stimulate the basal end vs the apical end of the basilar membrane?
High frequencies -> basal end
Low frequencies -> apical end
Once nerve impulses are initiated, the signals continue along the auditory pathway from the spiral ganglion cells within the cochlea to the ____, where the fibers form the cochlear branch of the VIII nerve
Modiolus
What is the first central connection for fibers coming from the cochlea?
Cochlear nucleus at the pontomedullary junction in the brainstem
What electrolyte is extremely elevated in perilymph and powers channels with shear on the hair cells?
Potassium
What is the general auditory pathway from CN VIII to the brain?
ECOLI Eighth nerve Cochlear nucleus Olivary complex Lateral lemniscus Inferior colliculus
A negative Rinne to a 256 Hz fork implies:
A negative Rinne to a 512 Hz fork implies:
A negative Rinne to a 1024 Hz fork implies:
Air bone gap of 15 Hz or more
Air bone gap of 25 Hz or more
Air bone gap of 35 Hz or more
What is the maximum output of a tuning fork?
60 dB
What is the most clinically useful tuning fork?
512 Hz - estimates 25-30 Hz air bone gap
Where does the tone localize with the Weber in CHL vs SNHL?
CHL: localizes to the affected ear
SNHL: localizes to the unaffected ear
Is a positive or negative Rinne seen in CHL vs SNHL?
CHL: negative–tone louder on mastoid
SNHL: positive–tone louder by ear
What does the Bing test evaluate?
Occlusion effect: fork placed on mastoid, occlude and unocclude EAC with finger, normally gets louder and softer but will remain stable in CHL
What are the symbols for unmasked and masked air conduction on audiogram?
O: Right unmasked air X: Left unmasked air
△: Right masked air ☐: Left masked air
What are the symbols for unmasked and masked bone conduction?
: Left unmasked bone
[: Right masked bone ]: Left masked bone
When should bone conduction be tested in pure tone testing?
When air conduction thresholds are 10 dB HL or greater
When should masking be done in air conduction?
When air conduction exceeds bone conduction by 40 dB or more for circumaural headphones or 70 dB for insert earphones
What should masking be done in bone conduction?
When the air-bone gap is greater than 10 in the test ear
What is a Type A tympanogram
Normal ear: peak at about 0 dekapascals, range from -100 to +100
What is a Type B tympanogram
Flat
Low volume: fluid in the middle ear
High volume: perforation or presence of tube
Very low volume: probe clogged or against canal
What is a Type C tympanogram?
Peak shifted to the negatives (-150 daPa or greater)
Negative middle ear pressure, retracted TM or eustachian tube dysfunction
What is a Type As tympanogram
Like Type A, but with an abnormally low peak, seen in otosclerosis, scarred TM, or malleus fixation
What is a type Ad tympanogram?
Like Type A, but with an abnormally high peak, seen with a flaccid TM or disarticulation of the ossicular chain
