Program

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Acoustics SeminarCatarina Hiipakka28.01.2015

Diagnosing Hearing Loss

Part 1: Hearing Disorders

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Some concepts

• Congenital

• Hereditary or genetic

• Acquired

• Pre- or Postlingual

Sensorineural

• Cochlea

• Auditory nerve

• Often hair cells, auditory neurons

• Threshold – where in cohlea

• Outer hair cells – common and mild to moderate

• Inner + Outer - severe

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Dead regions

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Don’t regenerate!No processingIC, neurons>50 dB

Not a dead region. OHC loss

Outer Hair Cells

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Also: Loudness recruitment

Sensorineural Hearing Loss

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• High frequencies

• Diplacusis – more than one pitch

• Loudness recruitment

• Presbycusis – age

• “I hear, but I cannot understand”

• Time resolution

Place theoryFrequency theory

Volley Principle

Conductive Hearing Loss

No distortion

No frequency specificity

Low level

Comfort in loud sounds, places – paracusis willisii

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Tinnitus and Hyperacusis

• Who has it?

• Subjective Tinnitus

• Objective Tinnitus: Circulation, temporomandibular joint, muscles

• 6 to 30% chronic tinnitus

• 1 to 2.5% clinically affected life

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Tinnitus and Hyperacusis

• 45% of tinnitus have hyperacusis

• 86% of hyperacusis have tinnitus

• Intolerance

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Other disorders

• Autosomal dominant inheritance• Autosomal recessive inheritance• Maternal infections, environment

• Head trauma• Impacted cerumen• Foreign bodies• Otitis• Otosclerosis• Retrocochlear disorders (brainstem)• Central auditory processing disorders

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Part 1: Wrap Up

Sensorineural Hearing Loss

Cochlear Dead Regions

Outer Hair Cells

Conductive Hearing Loss

Tinnitus

Others

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Part 2: Audiometry

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Normal HearingMinimum Audible Field

Minimum Audible Pressure

The Audiometer

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The Audiometer

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Bone Conduction

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More than an Audiometer!

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Hearing Level

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dB SPL to HL

Hearing Level

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Hearing loss at high frequencies

Normal (HL)

example

Audiometer Calibration

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ANIS/ISO Hearing Level – several standards

Audiometer Calibration

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Audiometer Calibration -Bone Conduction

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Artificial mastoid/mechanical coupler Test close-up

And Biological Calibration

Pure-Tone Audiometry

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1kHz 2kHz 4kHz 8kHz 1k 500Hz 250Hz

Pure-Tone Audiometry

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Results: Sensorineural and Conductive Hearing Loss

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Results

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Results: Considerations

Standing waves at 8kHz

Tactile responses

Acoustical radiations (bone conduction)

Collapsed ear canals

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Summing up: AUDIOMETRY

- Thresholds

- Level of hearing loss

- Sensorineural vs. Conductive

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Part 3: Other Diagnostic Procedures

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Acoustic Immittance

Immittance: Impedance, Admittance

Acoustic Immittance

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85dB 226 Hz probe tone

Acoustic ImmittanceTympanometry

varying pressure

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Otosclerosis

Scarred eardrums

Ossicular discontinuities

Middle ear fluid,Eardrum perforation

Eustachian tubedisorders

Acoustic Reflex

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Acoustic Reflex

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Speech Audiometry

• Speech audiometer

• Thresholds for speech• Speech detection• Speech reception (SRT)

• Signal-to-noise ratio

Words, syllables, sentences/several words

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Wrapping up

• Screening: Pure-tone air conduction

• Diagnosing: also • bone conduction, • tuning forks,• questionnaire, • speech reception, • acoustic immittance (if conductive)

• And more…

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Today’s question

How do you detect if a patient has conductive hearing loss?

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