Audiology

frequency

= pitch

in Hz

DB

= lousness

in decibles

Loudness measure

dB

dB- loudness in decibels

HL- hearing level

The higher the dB HL value, the louder the sound is perceived to be.

SPL

Sound pressure level

Loudness scale of dB HL

0 to 130

Threshold =

Quietest level of hearing

1k frequency level

Can detect all vowels at this level but cannot differentiate them

* cannot develop intelligible speech from this level

String bean line=

Demonstrates the area of highest probability for receiving the most information

Air conductive testing symbols

O X

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O air conductive symbol

Means the right ear

Demonstrated by red colour

X conductive testing symbol

Testing in left ear

Demonstrated by blue colour

Air conduction testing areas

Test middle and outer ear

Bone conductive testing areas

Tests cochlear only

Types of hearing loss

Conductive

Mixed

Neuro

conductive hearing loss

Middle or outer ear problems- air conduction testing

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Conductive hearing loss is a type of hearing loss that occurs when sound waves are blocked from reaching the inner ear. This can be caused by a variety of factors, such as earwax buildup, fluid in the middle ear, or damage to the eardrum or middle ear bones.

Sensory-neural hearing loss

Neuro hearing loss refers to hearing loss caused by damage to inner ear or VIIIth nerve - air conductive testing

air conductive testing in line with bone conductive testing results

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damage to the auditory nerve or the brain's ability to process sound. It can result from a variety of factors, including genetics, infections, head trauma, and exposure to loud noise. Treatment options may include hearing aids, cochlear implants, or auditory training.

Profound hearing loss definition

No spoken language

Can hear unidentifiable sounds

Bar-0 hz

Within normal limits

0-40 hz

Mild hearing loss

40-70 hz

Moderate hearing loss

70-90 hz

Severe hearing loss

90-130 hz

Profound hearing loss

Illnesses affecting hearing

Ototoxicity drugs given during cancer

Rubella

CVM disease - herpes virus type -cytomegalovirus

Lack of oxygen - hypoxia

Premature baby - antibiotics can damage hair cells in ear

Cortical reorganisation

Without auditory information sound- the brain reassembles to rely predominantly on visuals

Hierarchy of listening skills- Erber,1988

Detection

Conditioned/spontaneous awareness of sound

Discrimination of same or different sounds

Identification

Comprehension

Conductive areas

Middle and outer ear

Fixable

Sensory-neural areas

Cochlear

Unfixable

Linguistic sound detection

Aaaa

Ooo

Eee

Shhh

Ssss

Mmmm

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Say these sounds whilst covering mouth to see if child can detect them- demonstrated by hair NVC

Linguistic sound imitation

* identification early stages
* Occurs after detection

Cover mouth/sit behind child

See if they can imitate- Aaaa, Ooo, Eee, Shhh, Ssss, Mmmm

3 main areas of the ear

Outer

Middle

Inner

Outer ear function

Included The pinna, tympanic membrane and external auditory ear canal

Sound funnelling areas

Protection of the ear drum

Sound path to the ear drum

Collection of sound Localisation

Is S-Shaped

Middle ear function

Tympanic membrane

Ossicles chain

Eustachian tube

Mastoid spaces

* is the mechanical areas
* Increases the energy transferred from the tympanic membrane to the cochlea.
* Matches the impedance of the energy in the air to the impedance needed in fluids in the middle ear. 
* Barrier between outer and middle ear.

Inner ear function

Contains the Cochlear and vestibular organ( urticaria and saccule)

* sensory area

Pinna function

Part of the outer ear

• Elastic fibro-cartilage shell

• Lobule of fatty tissue

• Both covered by epidermis with fine hairs

• Extrinsic muscles to skull (controlled by VIIth nerve

• Intrinsic muscles to different parts of pinna (controlled by VIIth nerve)

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Physiology:

Collects sound an increases intensity for high frequencies (up to 6dBSPL). Directional effect

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Disorders :

Dermatitis/psoriasis

Malformed or absent Pinna

Collapsed ear canal

Injury e.g. ‘cauliflower ear’

Rodent ulcers/moles

External auditory meats canal

Part of the outer ear

Approximately 25mm long in adults

• Tends to be oval in shape 

• Cerumen glands in lateral third of canal

• Lateral third of canal is cartilaginous

• Inner two thirds is bony

• Slight constriction between the cartilaginous and bony section

• Bends and narrows along the length

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Physiology :

Funnels sound onto tympanic membrane Amplifies certain frequencies. Natural resonance of around 2.5kHz

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Disorders:

Wax

Otitis external

Artesian

Swimmers ear- osteomalacia

Polyps

Trauma –use of foreign object – cotton buds/hairpins/ objects inserted into ca

Tympanic membrane

Part of the middle ear

Pars Tensa –main area of membrane – 4 layers, 2 fibrous and 2 continuous membranes – taut.

• Pars Flaccida – upper portion – 2 layers, non- fibrous, thin. • Opaque appearance with cone of light (light reflex) originating from Umbo

• Handle of malleus visible

Middle ear disorders

• Otitis Media with Effusion

• Eustachian Tube Dysfunction

• Otosclerosis

• Mastoiditis (risk of meningitis)

• Glomus tumour

• Ossicular discontinuation

• Perforation

• Cholesteatoma

Ossicles

Part of the middle ear

• Ossicular chain acts as a piston, held taut by muscles. Amplifies sound

The muscles and tendons attached to the ossicles also help to protect the ear from very loud noises but also improves the sound by attenuating it 

• Malleus – attached to tympanic membrane.

• Tensor tympani muscle attached to handle (manubrium) of malleus.

• Incus attached to malleus and stapes.

• Stapes attached to Incus at it’s head and the footplate of the stapes embedded in the oval window.

• Stapedius muscle attached to neck of stapes.

• Both the trigeminal and VIIIth nerve pass through the middle ear.

Mastoid cavity

Part of the middle ear

Is air filled

Honeycomb like air cells in upper part of cavity

Set in temporal bone

Connects to the middle ear

Increases volume of middle ear space

Eustachian tube

Part of middle ear

Connect middle ear to nasopharynx

• Equalises middle ear pressure

• Mucous membrane

• Lateral third is bony (and held open)

• Medial two thirds is cartilage – normally closed and opens by reflex (yawning, swallowing, sneezing)

Cochlear and vestibular organ

Part of inner ear

• Bony and membranous labyrinth

• Shell like structure

• 2.5 turns – flattens towards apex

• 3 chambers – scala tympani, scala media, scala vestibuli all filled with fluids.

• Basilar membrane in middle chamber with organ of corti. Basilar membrane increases in width from base to apex.

• Organ of corti includes inner and outer hair cells

Cochlear

Part of inner ear

Cochlea fluids:

• perilymph, similar to CSF (extra cellular), high in Na, low in K ions.

• Endolymph, similar to intra- cellular fluids (although extra cellular). Low in Na and high in K ions.

• Rows of stereocilia – tallest outermost; rigid actin filaments. • OHC (Outer Hair Cells) – in contact with tectorial membrane and supported at base.

• Inner hair cells – 1 row, with supporting cells

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Physiology:

Stapes acts like a plunger into the Scalia vestibuli

Round window allows release of pressure

Difference of pressure between these results in a deflection of the Basilar Membrane

Basilar Membrane vibrates

Vibration travels down the Basilar Membrane (due to shape/ anchor point at apex)

Maximum deflection results from travelling wave dynamics.

Basilar membrane

Part of the inner ear

•Place frequency –

High frequencies causes a greater response near the base

Low frequencies near the apex

All due to stiffness of Basilar Membrane 

Tuning curve of the cochlear can be determined from place frequency

Turning curve

In the inner ear in the cochlea

Determines frequency where travelling wave has peak intensity.

Tuning curves can be used to detect any ‘dead regions’ in the cochlea.

How the ear detects sound

The vibration of eardrum causes the ossicles to vibrate, moving sound along them And transferred into the cochlea when the stapes moves the vibration to the oval window

This causes the fluid in the cochlea to move, creating a wave that passes along the length of the cochlea

The movement of the fluid in the hearing nerve (cochlea) makes the long membrane (basilar membrane) move. This has the hearing nerve cells embedded in it (these are called hair cells) they are lined up along this membrane.

When the hair cells are stimulated by this movement of fluid they release an electrical impulse along the hearing nerve (VIIIth Auditory nerve). These impulses are sent to various parts of the brain to be ‘translated’

High frequencies are detected from the first turn of the cochlea and low frequencies at the apex.

Brains function in hearing

Hair cells stimulate VIIth nerve

Auditory pathway stimulated from cochlear nucleus to auditory cortex

Brain interprets sound and filtering mechanisms in neurological centres help to distinguish type of sound, localisation, intensity etc.

Vestibular organ

Has semicircular canals

Includes the urticaria and saccule

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Nerves in the saccule and utricle detect rotational movement and linear acceleration when the fluid moves over them.

Feedback to the neural system makes it possible to keep your eyes fixated on something whilst the head/body is moving

There is a connection between the semi circular canals and the muscles controlling eye movements

Conductive hearing disorders

Anything that stop sounds from the outer to middle ear

Sensory hearing loss

Anything stopping sound being detected in cochlea

Neural hearing disorders

Anything that stop sound getting to brain

Conductive problems in outer ear

wax, foreign bodies (e.g. beads, insects), collapsed ear canal atresia, microtia, infections, perforations of the tympanic membrane, bony growths or polyps.

Conductive problems in middle ear

Eustachian tube stops functioning due to infections and irritations such as nicotine or pollen, bony growth on stapes (usually adults -Otosclerosis)

Sensory problems

Hair cells be one damaged due to

• Noise – high sound pressures over a long period of time, or a sudden very strong sound like a blast.

• Measles, mumps, meningitis and some viral infections that affect balance as well.

• Lack of oxygen • Wear and tear – some people have damaged nerve cells as they become elderly thought to be caused by vascular problems or can be genetic.

• Chronic health problems - heart disease, diabetes, stress. • Certain types of medication and drugs (ototoxic)

Inner ear disorders

Age related hearing loss

• VIIth nerve tumours

• Trauma – noise exposure/ head trauma

• Labyrinthitis 

• BPPV

• Menieres disease

Congenital hearing loss

• Main causes of congenital hearing loss occur in the first trimester when the ear is still developing. Development can be disrupted during this stage.

• Main causes tend to be viral infections caught by the mother – CMV, syphilis, chickenpox, measles.

• genetic factors

Development of the ear

7th week of gestation= vestibular system, external auditory canal, middle ear cavity, Eustachian tube and Ossicles are almost fully developed.

20 weeks= the pinna is adult shaped, EAM fully formed, TM formed from 9 weeks, Ossicles fully formed, inner ear is mature and of adult size.

Air conduction

A mechanism of hearing

Sound passes through the outer middle and inner ear

Bone conduction

A mechanism of hearing

Bone vibration stimulates the cochlear directly

Pure tone audiometry

Measure of hearing sensitivity at different frequencies using different transducers

It is the single most sensitive measure that can identify pathology

Relatively cheap and quick to administer

Hearing threshold

Quietest sound heard by an individual

Pure tone audiogram

Used to measure somebody’s ability to hear sounds we usually want to compare them to “normal” thresholds

Uses adiometer consists of 4 controls: 

Frequency adjustment 

Attenuation adjustment 

Presentation switch 

Response button 

Bone conduction masked

Right ear symbol

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Bone conduction masked

Left ear symbol

\]

Uncomfortable loudness level

Right to left ear

Performing a pure tone audiogram to obtain hearing thresholds

there will be an intensity above which the person will respond and an intensity below which the person will not respond = Threshold lies between these two intensities

Method:

Start at an appropriate level

Reduce by 10dB after a positive response

Increase by 5dB after a presentation is not detected

Threshold: Lowest level at which responses are obtained 2 out of 3 times on ascending trials = (Hughson and Westlake method).

With children, other methods can be used – play audiometry using pegs on board, balls on stick, men in boat or other suitable objects.

Air conduction testing HZ order

Start at 1 kHz

2,4,8 kHz

500,250 Hz

Retest at 1 kHz before moving to next ear

Bone conduction Hertz test order

Start at 1 kHz .

2,4 kHz .

500 Hz

Masking

Used when there is a difference in either AC threshold in each ear of 40dBHL or more

(due to transcranial transmission – cross over),

or BC thresholds of 10dBHL or more

(transcranial transmission for BC is 0 – 5 dBHL).

Mixed hearing loss

Both conductive and sensory neural elements lost

bone and air conductive losses at differing degrees

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Auditory Brainstem Response ABR and Evoked response Audiometry ERA

used in neonatal screening and also for difficult and medico legal cases. Involves looking at the brain response to stimuli (clicks or pure tones). Electrodes placed on the head pick up the responses along the nerve pathway.

Methods for determining hearing levels

• Evoked response Audiometry (ERA or ABR)

• Cortical Evoked Response Audiometry (CERA) - for 13yo+

• Otoacoustic Emmissions (OAE) • Subjective – Speech Audiometry- acoustic signals generated from the normal inner ear, either in the absence/response of acoustic/electrical stimulation

Supra-threshold test

A speech test

Speech discrimination threshold will be higher than detection threshold

Requires speech comprehension rather than just detection of sound

Paediatric speech tests function

– Developmental level of speech understanding

– Child’s ability to produce speech sounds

– Confirmation of how well a child can hear with hearing aids or show which speech sounds the child is missing out on

– If a child presents with a non-organic hearing loss NOHL

Adult speech test function

To confirm the audiogram results (for NOHL) To determine any auditory processing disorders. As an additional test to determine if a hearing loss is conductive, sensory or neural

Calibrated speech test function

an estimate of broadband hearing thresholds

• diagnosing site of dysfunction (conductive, sensory or neural)

• A measure of disability (PTA does not always do this effectively)

• A means of measuring benefit (when fitting hearing aids)

Consonants frequency range- Initial

Nasal

Fricative

Stop

Approximants

Voiced

Consonants frequency range- final

Nasal

Voiced

Plural marker

Past principle

Consonant frequency range- place contrasts

prosodic shape and stress pattern,

syllables/syllable structure,

manner categories in consonant clusters

Congenital hearing loss syndromes

Ushers syndrome

Neurofibromatosis type 2

Muscopolysaccharidosis- hurler syndrome

Down’s syndrome - trisomy 21

Pierre-robin sequence

Treacher Collins’s

Waardenburg syndrome

Branchio-too-renal syndrome

CHARGE- gene mutation disorder

Foetal alcohol syndrome

Factors affecting hearing in pregnancy

Chickenpox

CMV - herpes

Group B streptococcus

Infections from animals- cats, sheeps, pig

Hepatitis B+C

HIV

Parvovirus B 19

Rubella

STI

Toxoplasmosis

Zika virus

Factors affecting ability to perceive, interpret and produce sound

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•The degree of hearing ability

•How well the brain interprets, filters and attenuates the sounds detected and the use of visual and proprioceptors to further aid interpretation.

•The sound environment – intensity of the sound, reverberation, signal to noise ratio, harmonic distortion, distance to the sound source, head shadow effect/ interaural difference.

•How we interact with the sound environment – tolerance of sound, the ability to produce sound ourselves.

how is sound presented

variations in air pressure then vibrates in vocal cords

trough

area of low concentration of wave

loudness is affected by

amplitude , distance from source, density of item, presence of resonating body

larger the surface area \=

the larger the sound

denser the item\=

the more sound

frequency means the

number of waves

small area \=

small sound and amplitude

more wave cycles\=

higher the pitch

pitch remains the same regardless of

size

what is the only thing that changes depending on size

loudness

sinosoidal

any wave having the shape of a sine wave \= S

cps\=

cycles per second (same as HTZ)

Frequency equation \=

cycle % time taken

frequencies tell us \=

if wave is a vowel or consonant

vowel and consonant wave form together to make-

complex wave (played at same time)

complex wave\=

any wave that is not a sine wave

sound at audible level production\=

vibrations move back and forwards- causing waves- waves enter eardrum vibrating it and moving cochlear

crest

area of highest concentration of wave

frequency\=

number of cycles in a second