Audiology(131) - Unit 1 Exam

Specific historical event (mid-20th century) that created a sudden need for hearing rehabilitation

WWII caused many noised induced hearing losses in veterans

(Post WWII - 1960, Audiology formally recognized as profession)

Why did WWII “hearing event” force Otology and Speech Pathology to collaborate?

To provide aural rehabilitation

Collaboration created audiologists (Hearing assessments, diagnostic examinations, rehabilitative care)

Degree Progression: The entry-level degree requirement from the start of the field to NOW(the present day)

Initially only needed Bachelor’s Degree

Then required Masters

• Coursework included Communicative sciences, electronics, and clinical practicum

NOW need Doctor of Audiology

• Every state requires to practice audiology

• 4 year program (including professional prep)

• instruction in hearing and speech science, anatomy and physiology of hearing and balance, counseling, electronics, and computer science

• last years focus on clinical practice

What is the current designator for the professional doctorate required to practice? (e.g., PhD, ScD, EdD, or AuD?)

AuD

The “Big Three” - Three regulatory categories

Licensure, Certification, Accreditation

Licensure:

o Voluntary or mandatory?

o Who issues it (State vs. National)?

Mandatory, Legal requirement in ALL states

Issued at state level

For California licensure (after Jan 1, 2008), how many hours of supervised clinical practicum are required?

300 hours of supervised clinical practicum in 3 diff clinical settings

• Must have AuD not masters

Certification:

o Voluntary or mandatory?

o Who issues it?

Voluntary

Issued by:

• ASHA offers CCC-A (Certificate of Clinical Competence in Audiology)

• ABA offers American Board of Audiology Certified (ABAC), pediatric, vestibular, etc.

Accreditation:

o Who does this apply to?

Graduate-level educational programs (Doctor of Audiology/Au.D.) and institutions

Voluntary

AAA (American Academy of Audiology) primary focus

• Advancing audiology services and public awareness.

• Continuing education programs, professional journals, annual conferences

The world's largest professional organization for audiologists

ASHA (American Speech-Language-Hearing Association) primary focus

• Standards, accreditation, continuing education.

• Professional development, networking, advocacy efforts.

Certifies both speech pathologists and audiologists

ADA (Academy of Doctors of Audiology) primary focus

Historically focused on the business aspects and interests of audiologists in private practice

From a physical perspective, how is sound defined?

A series of disturbances of molecules within an elastic medium

Define Sound Psychologically

Sound as an auditory experience perceived by the brain

In a longitudinal wave, particle displacement is _______ to the direction of wave propagation.

parallel

Transverse Waves

particle displacement is perpendicular to the direction of wave propagation

Ex: ripples in water

Frequency

Number of cycles (of a sound wave) per second (Hz)

Period

Amount of time taken to complete ONE cycle

Velocity

the speed sound travels through a medium

• In air is approx. 344 m/s (at 20°C)

Why does sound travel faster in steel than in air?

steel is a stiffer medium and molecules are more packed than air

• denser molecules = sound vibrations can travel faster

Damping

The loss of energy due to friction

difference between Light, Heavy, and Critical damping

Light - Slow decay of vibrations (gradual)

Heavy - Rapid cessation of vibrations

Critical - Vibration stops almost immediately after displacement (before oscillation)

Impedance component - Resistance

Friction (independent of frequency).

Impedance component - Reactance

mass = ?

stiffness = ?

frequency dependent resistance (Stores energy)

• Mass Reactance: Opposes high frequencies.

• Stiffness Reactance: Opposes low frequencies.

Brownian Motion

The random movement of air molecules caused by thermal energy

Amplitude

Height of the sound wave

• Maximum displacement of particles from their resting position

• directly related to loudness

Impedance

the resistance a medium offers to the propagation of sound

• depends on the medium’s density, elasticity, etc.

Decible (dB) scale

expresses ratio between two values

LOGARITHMIC, not linear

dB SPL (Sound Pressure Level)

measures intensity of sound/Physical pressure.

sound pressure = force of sound on a surface area

• Reference is 20 dacapasals

dB HL (Hearing Level)

the number of decibels above an average normal threshold at a particular frequency.

• Normalized to human hearing.

0 dB HL is the average threshold for normal hearing.

dB SL (Sensation Level)

The number of dB above a patient's auditory threshold

Tone presented (dB) - patients threshold = sensation level

• negative if going backwards

Ex: tone is presented at 50 dB HL & person's threshold is 5 dB HL,

• the sensation level is 45 dB SL.

Psychoacoustics

the perception of sound

• pitch, loudness, localization, masking

subjective perception of frequencies (Mels)

Pitch

• higher frequ percieved as higher pitch

Loudness (and units of measurement)

subjective perception of intensity of sound

(measured in phon or sone)

• Phon: equal loudness

• Sone: relative loudness

Localization

ability to determine the direction and distance of a sound source

Interaural Time Difference (ITD)

[low or high frequ]

difference in time it takes for a sound to reach each ear

• useful for low-frequency sounds.

(cue for localization)

Interaural Level Difference (ILD)

The difference in sound pressure level (SPL) reaching each ear

• useful for high-frequency sounds

(cue for localization)

A

Pinna (Auricle)

B

External Auditory Canal (EAC)

C

Tympanic Membrane (Eardrum)

A

Tragus

B

Antitragus

C

Concha

D

Helix

E

Antihelix

G

Lobule

A

Semicircular Canals

B

Vestibular Nerve

C

Cochlear Nerve

D

Cochlea

What are names for the outer ear?

pinna, auricle, ear

A

Malleus

B

Incus

C

Stapes

Function of the Outer Ear

funnel/gather sound, protection, resonance

EAC Resonance (enhances what range of frequencies?)

EAC functions as a resonator

• enhances sounds between 2000 - 7000 Hz

"quarter-wave resonator" effect of the canal boosts frequencies

How does the middle ear compensate for the impedance mismatch between air and cochlear fluid?

The “transformer” action

• transforms sound energy from air to fluid in cochlea

• tympanic membrane → oval window

  • lever action of ossicles amplifies sound pressure

    • (Total gain approx 30 dB)

Mid ear - Area Ratio

tympanic membrane’s larger surface area compared to the oval window concentrates sound pressure

Mid ear - Lever Action

ossicles = lever system amplifying sound vibrations

• M & I transfer sound vibes from eardrum → stapes → oval window → inner ear fluids

Mid ear - Buckling Action (increase pressure by ___ dB)

Flexibility of the tympanic membrane

• increases sound pressure by approx 6 dB

Mid Ear - Pressure Equalization

Eustachian Tube maintains equal air pressure WHICH optimizes movement of tympanic membrane and ossicles

• connected to the nasopharynx to allow for pressure equalization

Tonotopic Organization

where diff frequencies are detected in the cochlea

• could theoretically point to certain part and show where 1000 Hz is detected

Base: high frequ

Apex: low frequ

Inner Ear function

hearing and balance

Inner Ear Fluids - Perilymph

Found in Scala Vestibuli & Scala Tympani

• High Sodium (Na+), similar to Cerebrospinal fluid (CSF) in brain

Inner Ear Fluids - Endolymph

Found in Scala Media (cochlear duct)
High Potassium (K+)

Inner Hair Cells (IHC) function

(afferent or efferent?)

The true sensory receptors

• primarily responsible for sending auditory signals to the brain(afferent/ascending)

Outer Hair Cells (OHC)

enhance sound sensitivity and frequency discrimination (“cochlear amplifier”)

• efferent/tuning

Organ of Corti (location and function)

located on basilar membrane in cochlea

contains hair cells that convert mechanical energy into electrical signals

Vestibular system (function and contains..)

responsible for balance

contains: utricle, saccule, semicircular canals

Semicircular Canals function

senses angular acceleration (rotational movements).

• Anterior, lateral, posterior

Otolith Organs (Utricle & Saccule) function

Detect Linear acceleration (gravity/elevator)

and head position

Central Auditory Pathway (CAP)

(function)

responsible for transmitting neural signals from the cochlea to the brain

• crucial for perceiving sound meaningfully

Hearing Pathway - Air Conduction (AC)

sound travels through outer and middle ear → inner ear → nerve

• If AC is abnormal, problem could be anywhere in auditory system

Bone Conduction (BC)

bypasses outer and middle ears by vibrating the skull and directly stimulating the inner ear → nerve

Distortional BC

Direct vibration of the temporal bone compresses the cochlear capsule

Inertial (BC)

The ossicles (due to mass) lag behind the skull movement, moving the stapes in/out of the oval window

Osseotympanic (BC)

Vibrations of the ear canal wall radiates sound into the canal which is heard via AC route

• enhanced by occlusion effect

The Vestibulocochlear Nerve (= 8th CN)
[carries..]

carriers neural signals from cochlea → internal auditory canal → brainstem

The Vestibulocochlear Nerve (8th CN) STRUCTURE

Two branches:

• Cochlear/Auditory branch

• Vestibular branch

carriers 30,000 auditory and 20,000 vestibular nerve fibers

Auditory Branch (vestcoch nerve VIII)

carriers hearing information from cochlea

Vestibular Branch (vestcoch nerve VIII)

carriers balance info from semicircular canals and otolith organs

Vestibulocochlear Nerve Pathway (branches, through)

BOTH branches travel from the inner ear → brainstem

• through bony tunnel called Internal Auditory Metus (IAM)

Tonotopic Organization of the Nerve

auditory nerve is organized by frequency

• High-frequ fibers (Basal): Derived from cochlea base, located on the outer portion(surface) of nerve trunk

  • tumors on outside of nerve often affect high-frequ hearing first beacuse they compress outer fibers

• Low-Frequ Fibers (Apical): derived from cochlea apex. located in center (core) of nerve trunk

The Junction (where does the auditory nerve (CN VIII) connect to the brainstem?)

Cerebellopontine Angle (CPA)

• this is junction of Cerebellum, Pons, and Medulla

First Relay Station (in Central Auditory Nervous System)

(and function)

Cochlear Nucleus

• separates input based on frequ of sound

• where nerve fibers terminate

Afferent vs Efferent

Afferent (Ascending): signals travel from ear to brain (mostly inner hair cells)

Efferent (descending): signals travel from brain to ear (mostly outer hair cells)

• help with tuning and noise management