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55 Cards in this Set
- Front
- Back
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Prevalence of hearing loss
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3/10 >60 y/o
1/6 41-59 (baby boomers) 1/14 29-40 (generation x) 1.4 million <18 y/o 3/1,000 infants born w/ severe-profound hearing loss |
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myths
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-only affection old people
*65% are <65 y/o *>6 million 18-44 w/ HL *1& 1/2 million school age if i had HL my dr would have told me only 13% drs routinely screen |
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SLP skill sets
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-conduct screening tests
-interpret audiograms -troubleshooting of amplification or assistive technology -assist in the referral and access to audiological services as well as provide basic information |
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particle motion
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energy->vibration->medium->receptor
*need receptor *vibration and receptor are physiological measure |
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vibration and particle motion
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sound wave propagation is proportional to longitudinal propagation vs. transverse propagation
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compression vs. rarefaction
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compression: molecule cluster
rarefaction: molecule disperse |
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transverse vs. longitudinal
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transverse: wave in which the motion of the molecules of the medium is perpendicular to the direction of the wave
longitudinal: a wave in which the particles of the medium move along the same axis as the wave |
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dampening
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diminished vibration due to friction
*decreased speed across increase time |
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2 properties an object needs
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1. elasticity: tendency of material to return to original position after disturbance
2. inertia: an object in motion continues in motion |
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Mediums
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air: 344 meters/sec
water: 1497 meters/sec solid: quick |
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velocity
*subjective correlate: |
speed at which object travels
subjective correlate: pitch |
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speed/velocity
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depends on density of medium
air vs WATER HUMID vs dry air fresh vs SALT WATER |
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velocity formula
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velocity(m/s)= displacement(m)/time
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Acceleration formula
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acceleration(m/s squared)= change in velocity(m/s)/time
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periodic vs. aperiodic
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periodic: predicted movement, pure tone, simple harmonics, distinct pitch, narrow tuning, limited dampening, sine wave
aperiodic: unpredicted movement, no tone, excessive dampening, broad spectrum |
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amplitude vs. frequency
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amplitude: extent of vibratory movement (direct proportion to displacement)
frequency: # of complete oscillations/time in Hz(direct proportion to velocity) |
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Sine wave terminology
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physiological (objective): psychological (subjective
-frequency(HZ)->pitch -intensity (dB)-> loudness -amplitude-> loudness -phase-> cancellation |
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wavelength
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distance between 2 peaks
frequency=velocity/wavelength |
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phase
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-measured in degrees
-perceptional correlate is cancellation/reinforcement -360' in one cycle -"in phase"= reinforcement "out of phase": at 180' difference=cancellation |
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complex vibration
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combination of 2 or more waves
Periodic: tonal, repeats regularly with time(voice,singing,music) Aperiodic: atonal, no repetition with time(noise,static) |
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complex periodic sounds
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-component+component=resultant
-resultant depends on phase and amplitude of component -use reverse fourier analysis -finding the fundamental frequency(lowest component of resultant) and harmonics -domain of time vs domain of amplitude |
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fundamental frequency
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shapes resultant in complex waves, frequency remains same in resultant
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characteristics of complex waveforms
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Upper Band limit
lower band limit band width center frequency |
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filters
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high pass
low pass band pass band reject in terms of frequencies allow pass |
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decibel
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unit used to define sound intensity
1. involves ratios 2. utilizes logarithms 3. non-linear 4. expressed by specified reference levels 5. relative unit of measure |
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intensity
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w/cm2 amount of power per area
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sound pressure
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dynes/cm2 amount of force per area
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dBSPL 10^-16 w/cm2
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20Xlog (p/pu)=dBSPL
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dBIL .0002 dynes/cm2
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dBIL=10xlog(1/16)
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0dBIL
0dBSPL |
softest sound audible to humans
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dBHL
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determine hearing sensitivity
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dB reference levels
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0dBHL=normative referenced HL
0dBIL=10^-16 W/cm2 0dBSPL= .0002 dynes/cm2 never means absence of sound 0dBSL= # of decibels above a hearing level(subjective) |
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peripheral auditory system
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-entire ear except the brain
-pinna/auricle -external auditory meatus -tympanic membrane -ossicles -cochlea -vestibular system |
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central auditory system
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-brain/neural system
-central function |
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peripheral auditory system
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outer ear-> middle ear->(conduct vibrations to inner ear)-> inner ear(give sense of hearing and carry nerve signal to brain)
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Outer ear
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Pinna: shape of sounds and localization
External auditory meatus: 1/3 cartilage(outer), 2/3 osseous(inner), epithelium covering contiguous with the tympanic membrane, glands(cerumincus-wax,sebatious-hair,oil) |
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functions of the outer ear
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1. narrow canal and long canal protects from foreign bodies
2. ceruminous, sebacious glands lubricate and protect canals from infection 3. pinna orientation collects sound in front of listener better than sound in back 4. natural resonance increases sounds pressure ~15 dB @~3500 Hz |
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middle ear ossicles
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malleus, incus, stapes
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eustacian tube
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-provides aeration and drainage of ME
-equalizes pressure on both sides of TM -adults ~35 mm @ 45 degree angle -children ~2-mm more horizontal -upper 1/3 bone -lower 2/3 cartilage -isthmus meeting pt |
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middle ear
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tympanic membrane (separates middle and outer ear
ossicles eustacian tube |
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tympanic membrane
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(ear drum) 3 layers:
-outer/periph layer with epithelial cells from ear canal -inner/central layer mucous membrane from middle ear -in b/w layer tough fibrous, connective and radial tissue -held together by tympanic annulus=pars tensa -notch of rivinus=pars flaccida -semitransparent @55' angle create cone of light -umbo center of membrane; malleus attach |
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middle ear muscles
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stapedius muscle: smallest skeletal muscle in human body(pulls stapes down and back stiffen chain, inervated by CN VII)
tensor tympani: pulls malleus upward, inervated by CN V |
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functions of middle ear
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-regulate pressure change
-carries vibration from air-filled outer ear to fluid filled inner ear -30 dB loss -compensates by: 1. area ratio (~25dB)-large area (TM)->smaller area(oval window) 2. curved membrane(~6dB)-vibration involves greater displacement for curved membrane & less displacement for manubrium 3. lever system(~2dB)- malleus constitutes the longer leg of lever and the incus is the shorter leg |
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otoscopy
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exam visualize pinna,external auditory meatus,TM
otoscope: handle, head(light bulb magnifying lens), cone(in ear) specula: cover |
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auricle/pinna malformation
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anotia: absense of pinna
microtia: pinna small atresia: lack of canalization stenoses: narrowing of EAM -otoplasty used for protruding auricles only -spacers for mild cases of stenosis |
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inner ear
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sensory organ/cochlea
oval window/round window 3 portions: 1. scala vestibula 2. scala media (organ of corti) 3. scala tympani helicotrema spiral limbus vestibular system 8th nerve |
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cochlea
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outer duct of cochlea is osseus labrynth and covered with band of connective tissue called spiral ligament (3.5 cm and 2.5 turns)
inner duct is membraneous labrynth |
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inner ear fluids
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ENDOLYMPH
exists in scala media high in potassium ions colorlesss tasteless incompressible PERILYMPH exists in scala vestibula/tympani comparable to CSF high in sodium colorless tasteless incompressible |
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organ of corti
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in scala media
tectorial membrane tunnel of corti outer hair cells (3 rows) inner hair cells (1 row) |
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hair cells
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OUTER HAIR CELLS (mobile)
cylindrically shaped ~12000 steriocilia at apex embedded into tectorial membrane mechanical fine tuning due to motility 5% go to brain INNER HAIR CELLS flask shaped ~3500 steriocilia at apex NOT embedded into tectorial membrane stationary 95% go to brain |
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hair cell transduction
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-the displacement of the basilar membrane due to vibration of the perilymph in ST creates the outer hair cell steriocilia to shear against the tectorial membrane
-Excitation: opening of pores causing - ionic flow into the highly + charged endolymph -Inhibition: shearing in opposite direction closes pores and stops the flow of ions -the release of neg. ions into the pos. charged endolymph is accepted by the stereocilia of the IHC and gives rise to electrical potentials -therefore conversion of mechanical energy to electrical energy is induced by shearing motion of the OHC=cochlear michrophonic -OHC motility allows for an increase in the chemical response which allows inner hair cells to react even with low intensity stimulation |
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theories of hearing:
Hemholtz vs Rutherford |
Hemholtz:
-BM has segments that are HZ tuned due to tension -Vibrations would move BM and OHC at diff. segments and frequency selectivity -does not account for dampening due to sharply tuned BM -does not account for seperation of quick stimuli Rutherford: -BM vibrates as whole and HZ selectivity occurs at higher neural stations -Does not account for frequency specific HL -does not account for refractory period |
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Central auditory pathway
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cochlea->auditory nerve(some end at ventral and dorsal nucleus)->superior olivary complex(1st decussation, some end)->lateral lemniscus->inferior colliculous-> medial geniculate body->course auditory cortex(sound given meaning)
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vestibular system
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3 systems of balance:
visual system proprioception vestibular |
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development of the ear
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-begins at 3 weeks gestation
-vestibular portion develop earlier than auditory 4 week:pinna 9 week: cochlea turns complete 10-12 week: organ corti begin form 16 week: cochlea adult size 24 week:ossicular chain ossify |
