Technique for identifying people who might

 have a particular disorder

Tests for it are quick, reliable, tolerable

SLPs: 3 years through adults b/c there are specialized equipment and techniques only audiologists can do.

AuDs: any age group 

Support personnel 

- birth through 6 months and 3 years to adult

 - supervised by a certified audiologist

- more cost effective on large-scale screenings (like newborns)

Newborn to 6 months

• ABR (Auditory Brainstem Response) and/or OAEs (Otoacoustic Emissions)

7 months (babies can turn their heads-visual enforcement) through 5 years

• Behavioral testing, frequently special techniques

Adults

• Behavioral testing

7 months - adults

Not looking for threshold

No change in intensity level

• Method: Present tones at a fixed level, see if they hear them

– Kids: Usually 20 dB HL (can be 30 dB HL for a particular technique)

– Adults: Usually 25 dB HL – Frequencies: 1000, 2000, 4000 Hz

• hear all, they pass

• miss any, they fail

Infants – Within 3 months of birth – Any time the parents are concerned

Preschool and school children – When they start school – In K, 1st, 2nd, 3rd, 7th, 11th grades – Anytime anyone is concerned

Adults – Every 10 years to age 50; every 3 after

Pass – Hearing is likely to be within normal limits – No need for further evaluation • Unless there are significant concerns

Fail – Hearing is likely to be impaired – A full hearing evaluation is needed

1. Brief case history (if any)

2. Otoscopy (sometimes)

3. Tympanometry (sometimes)

4. Pure‐tone screening – 1000, 2000, 4000 Hz only

– Presented at a single level only: 20dB for a child, 25dB for an adult

Very different from a full evaluation

1. Case history

2. Otoscopy

3. Tympanometry and acoustic reflexes

4. Pure‐tone audiometry

5. Speech threshold tests

6. Suprathreshold speech tests

7. Sometimes:

    Tests of loudness growth 

    Special audiometric/audiologic tests: ABR & OAE

May provide information regarding:

Expected test results

Cause of hearing loss

The interview process builds rapport:

Reduces patient stress

Relationship between patient & audiologist is key to later success with rehabilitation

1. Why are you here today?

2. Hearing loss history

– Duration

– Onset

– Severity

– Difficult situations

– Hearing aid experience

3. Family history of hearing loss?

4. Otological history

– Middle ear disease or surgery?

– Noise exposure?

– Tinnitus (ringing in the ears) or vertigo (balance)?

5. General medical history

– Head injuries?

– Serious illnesses?

– Current medications

Make them fill out forms, makes sure you cover everything. Go over it with them. Builds rapport and thoroughness.

• Done after case history, before anything else

– Good info re: general health of ear

– Helps you know whether or not to do tympanometry (test of the middle ear)

– Helps you determine whether and/or how to use insert earphones

• Two broad classes of otoscopes

– Hand‐held and video

• Instructions to patient

– All patient instructions should include:

1. What the audiologist will do and why

2. What the patient should do

• Technique

– Gently pull pinna to straighten the external auditory canal

For adults, pull up and back

For children, pull down and back

– Gently insert speculum, THEN look

– Examine shape and condition of ear canal

– Examine the ear drum, rotating otoscope to view all edges

• Definition: Assessment of hearing ability

– Sensitivity (how well a person hears)

– Ability to understand speech

• Some general considerations

– Test environment (quiet classroom, library)

– Instructions

– Room setup (don't let them see you or what you are doing)

– Transducer placement (on properly)

pure tone - one frequency, 1 sine wave

(oscillator) – located internally

– Discrete “audiometric frequencies”:

Standard Octaves: 125 – 8000 Hz

Inter‐octaves: 750, 1500, 3000, 6000 Hz

– Ultra‐high frequency audiometers:

Up to 16 kHz

– Controlled by the frequency selector switch

– Controls the intensity of signal

– Usually set in 5‐dB steps

Sometimes 1 and 2.5 dB also

– Range: ‐10 dB HL to maximum output level (depends on frequency)

Varies with frequency and output transducer

– Controlled by the attenuator dial

– Controls duration of signal

– Two modes:

“Normally off” for pure tones

– Push switch to present signal

“Normally on” for speech

– Push switch to turn signal off

– For pure tones, choose type of tone:

steady (continuous beep), pulsed (beep, beep, beep), or frequency modulated (FM)

Pulsed is BEST

– Transducer definition:

Converts the electrical energy generated by the oscillator to acoustic or vibratory energy

– Acoustic Transducers:

Earphones (Circumaural, supra‐aural or insert)

Loudspeakers

– Vibratory Transducers:

Bone‐conduction vibrator (sits on the mastoid bone, tells us how well the cochlea works, vibrates the osseous labriynthe)

• Noise generator for masking

– Frequency selector and attenuator dials change frequency and intensity of noise

- put a noise in the ear we are not testing to help mask background noise

External inputs (used for speech testing)

– Microphone (live speech)

– CD or tape player (recorded speech)

VU (volume unit) meter

– Used to monitor external input levels (tell you how loud the signal is, needs to hover around 0dB)

Response button

1. Earphone enclosures

▬ Can affect calibration

▬ Bulky/uncomfortable for kids

▬ Don’t help bone conduction

2. Insert earphones 

Comfortable (Kids and Adults)

▬ Doesn’t help when doing bone conduction testing to eliminate background noise 

Side benefits

• Collapsible ear canal problem (common in elderly ppl)

• Infection control

3. Sound‐treated rooms(aka sound booths) - anacoic chamber

• The preferred solution

• Can have 1‐ or 2‐room setup

• Not soundproof,

• Very quiet, isolated from external noise 

Does help bone conduction

• Very (!) expensive

▬ Ventilation can be a problem

• Ideal setup for diagnostic audiometry:

– Two rooms with a big window in between

– Patient side is double‐walled sound‐treated booth

– Tester side may be single‐or double‐walled

– Communicate over the audiometer (talkback) and/or via an intercom

• Key components for threshold tests

– What they’re going to hear

– What to do when they hear it

– Importance of guessing (they need to answer when they "think" they hear it)

• Possible responses for pure tones

– Raise hand

– Press response button

– Game responses (pediatric patients)

– Check for collapsing canals

– Open band all the way

– Push hair out of the way, remove earrings, eyeglasses

– Direct diaphragms to canal opening (direct microphone directly at the concha)

– Hold phones to ears, then adjust band

– Be sure to look in ears first!

– Clip transducers to shirt or hang on cord (Rght=Red, Blue=Left)

– Roll down the foam plug

– Insert gently into ear canal

– Hold in place until plug has expanded

– Note: At any location, bone conduction always stimulates and/or may be heard in both ears

– Mastoid process

– For normal‐hearing listeners, signal is loudest here  Close to the test ear

• By far the most popular choice

– Forehead 

Easier to place 

Results are less variable 

More comfortable 

Can keep glasses on 

Reminds you that you don’t really know which ear you’re testing!

Clinical Threshold Definition:

– The lowest level at which patient correctly responds 50% of the time

• Note: We use a 5‐dB step size

– “True” threshold may be between steps

– Measured threshold: the lowest level where patient is at least 50% correct

• 5 dB above measured threshold, they should always respond (100% of the time)

• 5 dB below, they should respond less than 50% of time (should never respond) 

Note: Listening at threshold is very difficult

– General principle: Make it as easy as possible for the patient.

• Test better ear first

• Test more easily heard sounds first

1. Start at 30 dB HL (1000Hz)

a. If patient does not respond: go up to 50 dB HL

– If patient still doesn’t respond: go up in 10 dB steps until patient responds b. If/when they respond: go down 10 dB

2. Go down in 10‐dB steps until patient stops responding 3. When they stop responding

a. Go up in 5 dB steps until they respond again

4. When they respond, go down 10 dB

5. Continue with down 10, up 5 until you find their threshold

• Threshold = Level where they respond to at least 3 out of 6 (i.e., at least 50% of) presentations

Start at 1000Hz, then 2000, then 4000, then down to 250 and 500Hz

AC = Air Conductor (transducer)

BC = Bone Conductor

Red, Round, Right

Red, Tri, Right

Blue, X, Left

Blue, Square, Left

when sound presented in a hearing test is heard by the non-test ear

AC: signal from earphone sets bones of head in vibration. Can stimulate opposite ear if signal is loud enough

BC: vibration always stimulates both cochleas, never know which one

the loss of sound energy, in dB, that occurs when a sound crosses from the test ear to the non-test ear.

Varies as a function of frequency and trasnducer

AC: insert = +70dB

supra-aural = 40dB

BC: 0dB

a change (increase) in the threshold of audibility for one sound casued by the presence of another sound

use narrow bands of noise in the non-test ear

Masking is needed at any frequency where the difference between the left and right notmasked air conduction thresholds is 40 dB or more when using supra or circum‐aural earphones or 55 dB or more if insertearphones are used.

• Supra‐aural ear phones for AC testing

– When ACtest –ACunmasked  40 dB

• Insert earphones for AC testing

– When ACtest –ACunmasked  55 dB

Masking is needed at any frequency where the not‐masked bone conduction threshold is greater than the air conduction threshold by 15 dB or more. The worse ear (by air conduction) would then be the test ear and the better ear would be the non‐test ear to be masked.

• Bone conduction testing

– When ACtest – BCunmasked  ≥ 15 dB

– Same as: whenever air‐bone gap ≥ 15 dB

– If you keep raising the masker level after the plateau, threshold will shift again

– The masking noise presented to non‐test ear crosses over to the test ear

– When size of the air‐bone gap is close to amount of interaural attenuation

• i.e., bilateral conductive loss of 40 dB or more

– Very hard to mask without overmasking

1. Get threshold in test ear

2. Add masking noise to non‐test ear – If threshold doesn’t change, you know the threshold was good (it was the test ear) – If it does change, increase masker level in 5 dB steps until you find 3 steps with no change (that’s a plateau)

3. Threshold measured in this plateau is correct (it was the test ear)

– Degree of hearing loss

– Configuration of hearing loss

– Type of hearing loss

• Normal (< 20 dB HL)

• Mild (21‐40 dB HL) – Special consideration for children; 15 – 25 dB thresholds would be slight hearing loss

• Moderate (41‐55 dB HL)

• Moderately Severe (56 – 70 dB HL)

• Severe (71‐90 dB HL)

• Profound (>90 dB HL)

• Flat

• Sloping (worse in highs)

• Rising (worse in lows)

• Steeply sloping

• Cookie bite

• Corner

• Conductive

• Sensorineural

• Mixed

Conductive hearing loss

(CHL)

– AC thresholds: loss

– BC thresholds: WNL

– AC – BC = Air‐bone gap

• Indicates amount of

conductive loss

• i.e., the size of the

conductive component

Sensorineural hearing loss (SNHL)

– AC thresholds: loss

– BC thresholds: loss

– No air‐bone gap

• i.e., AC = BC

problem is at the cochlea

Mixed hearing loss

– AC thresholds: loss

– BC thresholds: loss

– Air‐bone gap

• BC loss = sensorineural component

• Air‐bone gap = conductive component

Both hearing loss at cochlea (BC) and middle/outer ear(AC)

– Average of AC thresholds at 500, 1000, 2000 Hz

– Use to predict threshold for speech

– Tells about degree of communication impact

– Average of Best 2 AC thresholds at 500, 1000,

2000 Hz

Requires a patient to respond, their cooperation, and a behavioral response

ex. raise hand, push button, repeat words

Require some cooperation but no behavioral response

Ex. tympanometry, acoustic reflexes, otoacoustic emissions, auditory brainstem responses

Speech-Discrimination or Word-Recognition Tests

• May listen to single words, sentences, nonsense syllables.

 • May be in quiet or in background noise

the lowest level at which client can just detect speech 50% of the time.

• Materials:

– Numbers, words, syllables, running text, nonsense syllables, etc.

– Speak in rapid monotone

• Response:

– Raise hand or push button when hear your voice

• Procedure

– Instruct patient

– Start at a comfortable level, a level where you know they hear you

– Use the “Down‐10 Up‐5” Procedure to find SDT

• SDT: level where they respond 3 out of 6 times (50%)

• Instructions important:

– They need to respond even if they only think they hear you. 

the lowest level at which client can barely understand speech 50% of the time.

Materials: Spondees – 2‐syllable words with equal stress on each syllable

• VU meter important!

– Audiologists usually have mental list of 10‐12 spondees – Examples: hotdog, baseball, ice cream, downtown, etc.

• Response: Repeat the words or point to a picture

• Procedure: 2 Parts

Part 1: Familiarization and instruction

• Present 10 to 12 words at level where easily heard

• Want the words to be highly familiar

– use substitute words if miss words during this step

• Person instructed to repeat words

Part 2: Threshold search

– Instructions

• Person told will hear same words but will be softer

• Should repeat even if just barely hear

• Guess if not sure

– Using same 10‐12 words, follow the “Down‐10 Up‐5” Procedure

• Correct response, go down 10 dB

• Incorrect response, go up 5 dB

• Bracket to find level where hear 3/6 words

– Patient has limited skills in test language:

• Non‐native speaker

• Aphasic

• Young child

• Mentally disabled adult

– Patient is unable to understand speech at any presentation level

• Profound hearing loss

• Extremely poor speech understanding

• Aphasia

– Need VU meter to peak at 0 on each syllable

• Practice makes perfect

– Cover mouth

– Make sure using 10‐12 words

• 4 words = SDT

– Make sure you can understand person’s responses

– If you have an accent that differs from client’s (or vice versa) the SRT and PTA may not agree ‐ interpret accordingly

Speech Audiometry Equipment

Speech Audiometer

• not a separate device

• a circuit on audiometer that allows use of a speech stimulus

– Requires Sound Booth

• Quiet room for threshold testing

• “Isolation” from tester’s voice

– Requires that you hear the client/patient’s answers

• Microphone “inside” booth

1. Recorded

• Materials on CD, tape, computer files

• Presented through audiometer

• Standardized recordings of speech materials – may have norms

2. Monitored Live Voice (MLV) 

Tester speaks test materials into a microphone 

Tester uses the VU meter to monitor level of his/her voice

– Goal: maintain relatively equal intensity for all words

Why test sensitivity (threshold) for speech?

– Speech is the most important sound in environment

– Speech threshold ≠ everyday communication

- important check of pure-tone thresholds

Why test sensitivity to speech before puretone

thresholds?

1. Speech materials more meaningful than pure tones  Listening at threshold is difficult 

Starting with a familiar stimulus (speech) may be easier

For kids: speech is more engaging that just tones. Ex. animal noises

2. Speech tests confirm validity of pure‐tone results  Cross‐check principle

– Speech and pure‐tone thresholds should agree with one another

– If they don’t, something’s wrong

3. Speech threshold results may change your puretone test approach

 Which ear first?

What starting level? 

– Flexibility in selecting materials

– Can give visual cues when familiarizing them with test procedures.

– Variability across voices less of an issue at threshold level 

– SRT tells us about speech understanding at threshold

– SRT doesn’t assess speech understanding in more typical listening environments

Why assess speech understanding?

1. May provide diagnostic information about hearing loss.  Speech testing may tell you about function of the auditory nerve and central auditory system 

E.g., Poor than expected speech recognition abilities often seen in

– 8th nerve tumors

– Central auditory processing disorders

2. May provide information regarding impact of hearing loss on communication. 

How much trouble is person having?

– Pure tone thresholds only tell us about audibility.  Useful for counseling regarding hearing loss. 

Help in determination of hearing aid and/or cochlear implant candidacy.

– Sometimes want to know how patients might perform in challenging listening conditions

– Can add background noise to test environment

– When this is done the relative intensity of the signal and the noise is specified as the signal-to-noise ratio (SNR)

– SNR is the difference in intensity between the signal and the noise

– not actually a ratio

Speech: 50dB Noise: 40dB SNR: +10

Speech: 40dB Noise: 55dB SNR: -15

the patient may select an answer from an infinite number of possible utterances.

they are harder to perform

– Lists of words in which the phonetic content of

the list is representative of everyday speech

- hard to balance words phonteically

– PB word lists presented in an open-set response format

– CNC word lists (10 lists of 50 words)

– Northwestern University Test No. 6

• NU-6 Word Lists

– Central Institute for the Deaf (CID) W-22

• W-22 Word Lists

– Both the NU-6 and W-22 tests have 4 lists of 50 words

• Ideal: Test speech recognition with all 50 words

– Better reliability

– More sensitive to changes over time

• Note: Many audiologists use half lists (25 words)

– Patient chooses from set of possible responses

– Some closed-set tests focus on specific phonemes or features

1. Modified Rhyme Test (MRT) 

50 items with 6 alternatives

2. California Consonant Test (CCT) 

100 items with 4 alternatives 

Designed to target errors that are likely in high frequency SNHL 

Example: – “Check the word ___________.”

(pail, tail, fail, sail)(date, bait, gate, wait)(kill, pill, chill, till)

3. City University of New York (CUNY) Nonsense Syllable Test (NST) 

VC and CV syllables, 7-9 alternatives 

“You will mark, ____, please” 

Difficult test, more often used in research.

– Considered more representative of everyday speech than single words

- people tend to do better on these because of context and content

1. CID Everyday Sentences

– Lists of 10; open set

2. Speech Perception in Noise (SPIN) Test

– Assesses use of context

» LP (Low probability) and HP (High probability)sentences

» “The dog gave a warning growl.”

– Presented in background of 12-talker babble (+8 dB SNR)

3. Hearing in Noise Test (HINT) 

Level of sentences adjusted, background noise constant  Finding RTS (Reception Threshold for Speech)

– RTS = SNR where person gets 50% correct 

Noise level fixed (65 dBA), azimuth varies

– Noise to front, left, and right sides

-used in cochlear implant patients, <50% on this test, then a great candidate for cochlear implant

4. Speech in Noise (SIN) Test 

Sentences presented at various fixed SNRs 

6 sentences in the presence of 4-talker babble 

5 key words per sentence 

Sentences are presented at pre-recorded SNRs from easy to very hard listening conditions

– CNC/NU-6 can be used with ages 8 and above

– Phonetically Balanced Kindergarten Test (PBK) (Haskins, 1949)

– LNT/MLNT word tests (Kirk et al. 1995)

• Lexical effects are controlled (easy vs. hard words)

• Easy words (occur often in English and can’t be easily confused with other words, e.g. door, food, watch)

• Hard words (don’t occur very often and are easily confusable, e.g., hid, dad, ring)

- kids do better on these

– Word Intelligibility by Picture Identification (WIPI)

• 6-alternative, picture-pointing task

– Northwestern University Children’s Perception of Speech (NU-CHIPs)

• 4-alternative, picture pointing

– With both, need to make sure picture is in vocabulary

– To use recorded or MLV

– Test material to use

– Method of response

– Intensity to present the test

– Using more than one intensity level?

– Noise?

– Amount of noise?

– Ideal: Test at several levels to generate a performance-intensity (PI) function

• Plots % correct as function of level

• From this identify their “PB-Max”

– maximum score for PB words

– Reality: Time constraints limit testing to one level

• 30 to 40 dB SL is common.

– Scores for people with SHNL can be quite variable from one testing session to the next

– Could be a result of number of test items presented (variability decreases as number of test items increases) – Smallest variability should be seen from people who always perform close to perfect or from those who perform close to 0%

– Greatest variability should be seen from those who perform in the mid-range

– Researchers demonstrated that two speech recognition scores in the mid-range from the same person may differ by 20% or more in order to be considered significantly different.

- has no formal steps

- lets them determine what is a comfortable listeing level (top and bottom) MCL and UCL

- useful for hearing aid fitting purposes

- if done before speech recognition, testing may determine presentation level for test.

– MLV, free running speech

– Adjust level until person indicates you’ve reached MCL

– Use an up-down method

– Many different procedures and instructions

– MLV, free running speech

– Increase level of voice until person indicates discomfort

(not pain)

– Drop and repeat

• The range of comfortable loudness (RCL) is the difference between the SRT and the UCL

• This difference is also called the dynamic range (DR) of speech/hearing.

• A normal hearing person typically has a DR of 100 dB or more.

SRT = 0dB UCL = 100dB DR = 100dB

SRT = 10dB UCL = 90dB DR = 80dB

SRT = -5dB UCL = 85dB DR = 90dB

Middle-ear measurements (not really directly taking measurements in the middle ear)

Impedence audiometry

Tympanometry - we are measuring how sound is transmitted through the middle ear-indirctly, trying to find out which pressure where your ear has the most compliance

If not sick, atmospheric pressure on either side of TM

1. Static acoustic compliance

• The mobility of the tympanic membrane in response to a given value of air pressure in the external ear canal

2. Tympanometry

• A measurement of the middle ear pressure

• Determined by the mobility of the TM as a function of positive and negative air pressure in the external ear canal

• The more positive or negative the air pressure in the external ear canal the more the normal middle ear system becomes immobilized.

3. Acoustic Reflex

• Can measure the contraction of middle ear muscles (stapedius mainly and tympani) in response to intense sounds

• The contraction of these muscles decreases the static acoustic compliance

- muscle contracts the stapes will not vibrate

• A moving object must overcome a certain amount of resistance to its movement

• A sound wave moving through the air will strike surfaces that impede or slow down its progress.

• The impedance of a medium is the opposition it offers to the transmission of acoustic energy

• As a surface that is placed in the path of a sound wave is made more dense, it offers greater impedance to the wave.

Infection or fluid cause impedance to the sound wave

Impedance high, Admittance low

1. Resistance (R)

• The force that opposes motion (e.g., friction)

• the resistance caused by a gas to the motion of a solid body moving through it (i.e., drag)

2. Reactance

• Similar to resistance but is influenced by frequency

• Opposition to energy transfer that varies by frequency

1. Mass Reactance

• As the physical mass of the object increases so does the mass reactance (a direct relationship)

• As the frequency of vibration increases so too does the mass reactance (a direct relationship between frequency and mass)

2. Stiffness Reactance

• As the physical stiffness of an object increases, so does the stiffness reactance (a direct relationship)

• As the frequency of vibration increases, stiffness reactance decreases (an inverse relationship)

Stiffness increases, Frequencies affected decrease

– independent of frequency

– friction effects

– primarily determined by ligaments supporting ossicles

– As mass increases higher frequencies become more

impeded (mass and frequency are directly related)

– primarily determined by weight of ossicles and

tympanic membrane

– If have disorder that causes more mass to ossicles

and TM what might happen? Fluid builds up and adds mass, high frequencies are impeded

– its contribution to impedance increases as frequency

decreases (stiffness and frequency are inversely

related)

– primarily determined by fluid pressure from inner ear

on the stapes, also stiffness of TM and air in middle

ear

– what would happen if increased stiffness of ME? Low frequencies are impeded

– reciprocal of impedance

• ease with which sound energy is transmitted

through middle ear

– Y = 1/Z

admittance increases, impedance decreases

– AKA Compliance

• The probe in the tympanometer has 3 tubes connecting it to

1. Loudspeaker 

Plays a probe tone – usually 226 Hz, 85 or 90 dB SPL

2. Microphone 

Measures the intensity level in the ear canal (comprised of both the probe tone intensity and the reflected wave as it returns from the TM)

3. Air pump

• Changes air pressure in ear canal

– Can create either positive or negative air pressure within the ear canal/outer ear

– Calibrated in milliliters (ml), millimeters of water (mm H20), or dekapascals (daPa)

– 1 daPa = 1.02 mm H20

– 1 mm H20 = 0.98 daPa

This is done AFTER Otoscopy, make sure there are no obstructions

– High admittance (low impedance)

• Most of probe energy (sound) passes through middle ear, very little is reflected

• High admittance = probe level in ear canal is low

– Low admittance (high impedance)

• More of probe energy (sound) reflected off TM, less passes through middle ear

• Low admittance = probe level in ear canal is high

• Step 1 (Performed by the clinician)

– Insert probe into ear canal

– Adjust as needed until you obtain an airtight seal

• Step 2 (Performed by tympanometer)

– Air pressure in canal is increased to +200 daPa, then gradually lowered to -200 daPa

– Microphone measures level of sound in canal and calculates admittance as a function of air pressure

– Admittance will be greatest where ear-canal pressure equals middle-ear pressure

• normally ≈ 0 daPa

+ pressure, TM stiff, High Impedance, Low Admittance

- pressure, Low Impedance, High Admittance

– The first measurement is taken when the ear canal is loaded with positive pressure and the TM in immobilized

– The next measurement is taken when the pressure decreases and the TM becomes mobilized (i.e., the pressure on both sides of the TM are equal)

– The static acoustic compliance is determined by subtracting the 1st measurement from the 2nd measurement.

• Performed by making successive measurements of compliance after negative pressure is presented to ear canal

 • Purpose is to determine the point and magnitude of greatest compliance of the TM

- most mobile TM, most compliant

A plot of admittance as a function of air pressure Key information

1. Equivalent volume or ear canal volume Computed from compliance at +200 daPa Reflects volume of ear canal

Normal values: 0.3 – 0.9 for kids 0.9 – 2.0 for adults

2. Peak compliance (static acoustic compliance, or static admittance) Height of the peak Indicates how mobile the tympanic membrane is Higher peak = better mobility Normal values: 0.3 - 1.7 mmho (or cm3)

3. Peak pressure Location of the peak Admittance is maximum when there is no pressure difference across the TM Indicates middle ear pressure, which reflects Eustachian tube function

Normal values: -100 to +50 daPa

Type A Tympanograms

[image]

Type B Tympanogram

[image]

• Type B = no peak at any pressure

– If volume is normal, indicates fluid in middle ear

– If volume is very high, indicates perforated eardrum

Type C Tympanogram

[image]

• Type C = normal compliance, but negative peak pressure (< -100 daPa)

– Indicates negative pressure in middle ear

– Caused by Eustachian tube dysfunction

- innervated by 7th cranial nerve - facial

• attaches to stapes via stapedius tendon

• contraction of this muscle pulls it away from the oval window

• the primary muscle involved in the acoustic reflex

- innervated by 5th cranial nerve - trigeminal

• may or may not be involved in reflex

• attaches to manubrium via tensor tympani tendon

• when it contracts it pulls the malleus away from the TM

• Both muscles stiffen the ossicular chain which changes the transmission of sound through the middle ear

• Primarily reduces low frequency transmission (inverse relationship for stiffness and frequency

• Contraction of the stapedius muscle in response to intense sound

• The reflex is bilateral

– Occurs in both ears in response to sound in either ear

• Clinically useful:

– presence/absence tell us the status of several parts of auditory system

• Protection – reduces intensity of sounds going into cochlea at and below 1000 Hz (impedes low fequencies)

• smoothes the frequency response of the middle ear system

- only occurs for a few seconds, shorter, intense sounds < 1000Hz

Arc = transmission of sound

• In the ear where the sound is being presented (stimulus ear):

– Sound pass from • outer ear through • middle ear to • cochlea

– Nerve impulses are carried along the • auditory nerve to the • cochlear nucleus, then to the • superior olivary complex (SOC)

If problems are at the outer/middle ear, it could effect the arc.

ipsilateral/contralateral response happens at the SOC ipsilateral/contralateral happen at the same time