audiology exam 1

lesions

abnormalities of structure +/ function in auditory system; cause of hearing impairments

idiopathic disease

specific underlying cause cant be identified

congenital disease

present at birth

hereditary/genetic disease

transmitted by genetic code inherited from parents

acquired disease

disease matter of causation

does nature of lesion correspond to severity + time course of hearing loss?

no

prelingual impairments

-occur before development of speech + language
-have catastrophic effect on this process
-longer time of auditory stim deprivation leads to more interference w/ development

postlingual losses

have relatively smaller effect

case history

-includes info that gives insight into auditory status + related factors
-contributes to making diagnostic impression, plan for remediation, referrals to other pros

what case history involves

-getting full pic of patient’s auditory + communicative status
-historical info abt factors known to influence/relate to auditory functioning
-patient’s pertinent med + fam history

chronological age

age since birth

mental age

individual’s cog ability in terms of age when avg normal person achieves same level of performance

gestational age

time period btwn conception + birth

conceptional age

child’s age measured from date of conception

developmental age

age in terms of level of maturation

prematurity-adjusted/corrected age

found by subtracting # of wks of prematurity from chronological age

sac + hhie-s

-included in asha screening guidelines for hearing disability
-scores are associated w/ various degrees of disability
-higher scores: greater degrees
-those who fail screening are counseled so they understand that they fall outside of norms

lowest stimulus levels that can be used in hearing test depend on?

ambient noise levels in testing enviro bc ambient noise can prevent test signals from being heard due to masking

how ambient noise issue leads to practical considerations for screening program

once test level is decided for specific goals of program a room must be found where noise levels are low enough to permit testing at that level

what if quietest available room has noise levels too high to permit screening at level appropriate for goals?

1) consider changing screening levels/frequencies so that they’re testable in that room
2) consider whether these screening criteria are justifiable w/in goals of our program

why its sig to include onset/progression, “in what sits do u notice most difficulty understanding others” and other relevant otologic history in case history

-speaks to functional impact of hearing challenges
-can guide testing decisions
-helps w/ counseling
-gives patient perception

case history purpose (for hearing impairment)

-nature: type, characteristics, possible etiology
-severity: patient’s perception of how they’re affected by it
-time course: includes how impairment has changed
-opportunity to build rapport w/ patient

methods of obtaining case history

-written questionnaire 
-patient +/ caregiver interview
-observation
-med records review
-secondary reports

other relevant otologic history

-abnormal perception of sound (tinnitus)
-ear pressure/fullness
-ear drainage

sig considerations for otologic symptoms

onset, frequency (intermittent vs constant), duration, affected ear(s)

whats included in med history

other diagnoses, meds, visual limitations, dexterity

considerations for pediatric pops (case history)

-source of info
-birth history
-fam history
-developmental milestone
-hearing + listening behaviors
-speech, language, academic concerns

outer ear parts

pinna, canal, ends at eardrum

part of ear classified as middle ear system

tympanic membrane (eardrum)

end of middle ear system

where ossicles transmit signal to inner ear fluids at oval window

shape of ear canal and clinical sig

2 curves forming slightly s-shaped pathway. usually requires straightening to view eardrum w/ otoscope

what underlies outer third vs inner two thirds of canal

outer: cartilage, inner: bone

functions of sebaceous/ceruminous gland secretions in ear canal

lubrication, antimicrobial action, keeping out debri

angle tympanic membrane tilted

55 deg

eardrum layers

outer layer continuous w/ ear canal skin, inner layer continuous w/ middle ear mucous membrane, 2 middle fibrous layers (1 radial, 1 circular)

otoscopy

thorough visual exam of outer ear, canal, eardrum

otoscopy sig

gives info abt condition of canal (cerumen, foreign bodies, infection), eardrum (intact, perforated, fluid), ensures safety + validity of procedures by being before other audiologic tests

pinna + eardrum parts

audiometer

electronic device that produces + delivers sounds to patient to evaluate auditory functioning; readings are consistent from device to device

what a pure tone audiometer must be able to do

produce pure tones at certain frequencies, precisely control the levels of these tones, deliver them to patient

single-channel vs two-channel (masking) audiometer

-single-channel can only make one sigal
-2-channel has second channel (w/ its own interrupter + attenuator) that makes masking noise

why hearing sensitivity in dB SPL isn’t the same at every frequency

phys intensity needed to just barely hear tone varies by frequency

RETSPLs

reference equivalent threshold sound pressure levels: normal reference spl values repping phys intensity needed by ppl w/ normal hearing to just reach threshold at each frequency using standard audiometric headphones

purpose of concept of hearing level (HL)

it’s inconvenient to use diff reference spl values at every frequency so it lets us use same convenient value (0 db) to rep normal threshold at every frequency

why all the diff restpl values can be considered equally audible

each retspl reps softest sound a person w/ normal hearing can just barely hear at that frequency even tho they have diff phys spls --> so theyre equivalent

the unit audiologists work in (spl/hl) for most clinical purposes + reason

hl bc spl conversions are handled automatically by audiometer’s circuitry, making spl “transparent” to clinician

screening (pure tone) audiometer

-simplest type made mainly for quick checks of hearing sensitivity
-limited test frequencies
-simple pass/fail results

clinical audiometer

-includes all features of pure tone audiometers + more
-wide range of frequencies + intensities
-multiple transducer outputs
-specialized tests

type 1 audiometers

-highest standard
-wide frequency range
-functions: air + bone conduction, speech testing, narrowband masking, advanced testing
-hospitals, audiology clinics
-very precise accuracy

type 2 audiometers

-slightly less diagnostic capabilities
-relatively wide frequency range
-functions: air + bone conduction, speech testing, some advanced testing
-clinics, ent practices, university training clinics
-high but not as much accuracy as type 1

type 3 audiometers

-basic diagnostic/screening-level
-limited frequency range
-functions: mainly air conduction, limited masking
-occupational health screenings, school screenings, mobile clinics
-accurate for screenings but not detailed diagnostics

type 4 audiometers

-lowest standard
-very limited frequency range
-functions: only air conduction, fixed intensity
-mass hearing screenings, community programs
-minimal accuracy (just identifies possible hearing loss)

audiometer controls

supra-aural headphones

-supra: on top
-used w/ clinical + screening audiometers

circumaural headphones

-circum: around
-good acoustic seal -> helps reduce bg noise
-can deliver high-frequency sounds more reliably than other headphones
-often used for extended high-frequency audiometry

insert earphones

-placed inside canal to deliver sound directly
-good acoustic seal

sound field speakers/loudspeakers

-deliver audiometer’s signal into enviro rather than ear
-essential for aided testing (eg hearing aids) or young kids who cant tolerate earphones

bone conduction vibrator

-converts audiometer’s electrical signal into mechanical vibration + delivers to skull
-bypasses outer + middle ear to stimulate cochlea
-usually placed on mastoid process
-stimulates both ears directly

db spl

phys measure of sound pressure

spl for ppl w/ hearing loss

-these ppl require higher spls than retspls values to just hear sound
-hearing is worse when their thresholds deviate from reference values more

masking

when presence of one sound interferes w/ ability to hear other sounds

diffuse field

type of sound field that has reflections resulting in same spls at all points w/in field; those w/ excessive reflections can negatively impact sound detection + speech intelligibility

ambient noise

bg sounds present in test enviro that arent part of test signal; can mask soft test tones esp at low frequencies

single-room booth

patient stays in booth while tester + equipment are outside

sound suite

has patient room + control room

test enviro construction

walls, ceilings, floors, doors typically made of 4-in. thick panels made of metal sheets filled w/ sound-attenuating material

other considerations for audiometric testing enviros

-doors close w/ tight seal
-incandescent lights
-prewired jack panels
-sound-muffled ventilation system

masking, frequencies, interference

given tone is masked most by noise close in frequency + lower frequency sounds can often mask higher frequency sounds

finding ambient noise level

-specify frequency range (bandwidth) to be considered around each frequency
-done in terms of octave-bands + 1/3 octave-bands

max permissible ambient noise level

-levels are measured w/ sound level meter that has set or octave/third-octave band filters
-these are then compared to mpanls specified by ansi standard

octave vs 1/3 octave band

octave is more conservative but less specific

octave-band level (obl)

spl w/in octave-band

max octave-band levels

-max ambient noise levels that allow normal-hearing patient to hear tone presented as low as 0 db hl
-actual noise level that exceeds max allowable levels by 15 db --> lowest measurable threshold in room = 15 db hl

pure tone

sound made of single frequency (smooth repeating sine wave)

complex tone

sound w/ 2/> frequencies (fund frequency + harmonics/overtones) (irregular, more complex

audiometry

measurement of hearing sensitivity

pure-tone audiometry upside-down triangle hierarchy level 1

detection: hearing smth

why test w/ pure tones?

pure tones are building blocks of all complex sounds + indicates amt of access to certain speech sounds (vowels/consonants)

consonants

-carry less energy (softer sounds)
-provide clarity + intelligibility of speech

pure-tone audiometry components

1.air conduction testing (natural way of travel)
2.bone conduction testing (bypass outer + middle ear)
3.clinical masking (if needed)

pure-tone audiometry: air conduction

-sound that reaches ear from outside starts as air conduction signal
-interacts w/ ur auditory system
-signal originates from transducers
-air conduction testing tests whole auditory system

if fluid blocks middle ear when air conduction testing

sound has to fight thru fluid --> loses energy

pure-tone audiometry: bone conduction

-sound also causes vibrations thru skull that directly stims cochlea
-can give info on integrity of cochlea + subsequent auditory pathway
-tests sensory (cochlea) + neural (auditory nerve pathway) systems
-not ear-specific (sends vibrations across whole skull)

pure-tone audiometry air conduction testing considerations

remove interfering artifacts (glasses, jewelry, etc)

pure-tone audiometry bone conduction testing considerations

-remove artifacts
-decide btwn placement of oscillator on mastoid/forehead
-identify structural abnormalities that can interfere w/ placement

bone conduction occlusion effect

-un-occluded (ideal): testing w/o ears covered
-additional vibrations of cartilaginous portion of canal is released out canal
-occluded: vibrations in cartilage of canal cant escape, bounces around and goes back into canal --> overrepresentation of sound occurs
-doesnt occur when bony portion of canal is blocked
-stronger signal reaches cochlea when ear(s) covered

bone conduction occlusion effect ii

-cartilaginous walls primarily add low-frequency energy
-low-frequency sounds have longer wavelengths that can get trapped + boosted when canal is blocked
-high-frequency sounds are less affected + shorter wavelengths --> quicker absorption

sound intensity (loudness)

-unit: uPa (micropascals)
-damaging sound level: 2 × 10^8 upa
-intensity is described as ratio
-20 upa = 0 db (smallest sound?)

sound intensity: db

-db = unit for intensity/pressure
-db are compared to reference value (20 upa)
-db spl: physical intensity

pure-tone audiometry

measure of hearing sensitivity at individual frequencies

pure-tone audiometry upside-down triangle hierarchy level 2

discrimination: hearing this not that sound

pure-tone audiometry upside-down triangle hierarchy level 3

identification: i heard this (but might not understand it)

pure-tone audiometry upside-down triangle hierarchy level 4

comp: hearing + understanding

vowels

-carries most acoustic energy of speech
-provides loudness + power of speech

frequency

no. of cycles/sec

intensity (loudness)

power of a sound per unit area, proportional to square of amplitude

amplitude

max displacement of air particles from their resting position during sound vibration

smallest pressure that humans can hear + damaging pressure

20, 2×10^8 uPa

why are dB used for audiograms

-range of human hearing is so great that no.s used to describe intensity can be cumbersome + hard to convey
-range is described as ratio to compensate
-w/ specified reference point

intensity dB

-dB: unit for sound intensity/pressure
-expressed on logarithmic scale
-db spl: physical intensity of a sound, measured in db, in reference to softest sound avg young human ear can detect (20)
-every 10 db increase reps 10x increase in intensity (+ perceived roughly 2x loud by ear)