Download CSD 3000 DEAFNESS IN SOCIETY

CSD 3000
DEAFNESS IN SOCIETY
Topic 2
HEARING
Sound System
Source

Any vibrating object
Medium

Any gas, liquid or solid
Receiver

anything designed to
detect the vibrations
within the medium
originating from the
source
A Common Sound System
Illustration of the
distribution of
molecules
surrounding a
source in an instant
in time
Condensation and Rarefaction
Bands of condensation
and rarefaction
emanating from a
sound source
Propagation of a Disturbance
Through a Medium
Notice that as time goes on, molecules farther from the
source become affected by the disturbance.
Important Physical
Characteristics of Sound
Frequency



Rate of pressure
change as a
function of time
Measured as
cycles/sec or Hertz
The primary
determiner of pitch
Intensity



Magnitude of the
pressure change
Measured as the
decibel (dB)
The primary
determiner of
loudness
Frequency and Intensity
Sounds a and c share
the same frequency
and sounds b and c
share the same
intensity
Loudness and Intensity
Here are some common sounds and their
decibel equivalents
The Hearing System
Basic schematic diagram of the entire auditory
system
The Outer Ear
Major Landmarks:
1.
2.
3.
Pinna
External Auditory
Meatus
Tympanic Membrane
Function of the Outer Ear
1. Collect and funnel sound to the
eardrum
2. Protection
3. Resonance
The Middle Ear
Major Landmarks:
1. Middle Ear Space
2. Eustachian Tube
3. Mastoid
4. Oval and Round
Windows
5. Ossicles
Function of the Middle Ear
1. Amplifier and transformer
2. Protection
The Inner Ear
Major Landmarks:
1. Bony Labyrinth
2. Membranous Labyrinth
3. Auditory and Vestibular
Portions
4. Cochlea
The Organ of Corti
Central Auditory Pathways
Putting It All Together….
Causes of Hearing Loss
Ways to Categorize Etiology:
1. By Site of Lesion



Conductive Hearing Loss
Sensorineural Hearing Loss
Central Auditory Processing Disorder
2. By Time of Onset


Congenital vs. Adventitious
Prelingual vs. Postlingual
Hearing Loss in Children
Prelingual Causes
1. Genetic

Nonsyndromal
Recessive Hearing
Losses
Nonsyndromal Recessive
Hearing Loss
Heredity Pattern
Implications:


No family history
Most members are
carriers of the
disorder
Hearing Loss in Children
Prelingual Causes
1. Genetic


Nonsyndromal
Recessive Hearing
Losses
Syndromes
Hearing Loss in Children
Prelingual Causes
1. Genetic
2. Premature birth and/or
complications during
delivery
Hearing Loss in Children
Prelingual Causes
1. Genetic
2. Premature birth
and/or
complications
during delivery
3. Prenatal Infections





Rubella
Cytomegalovirus
Herpes Simplex
HIV
Toxoplasmosis
Hearing Loss in Children
Postlingual Causes


Viral Infections
Otitis Media
Adult Onset Hearing Loss
1.
2.
3.
4.
5.
Noise Exposure
Presbycusis
Ototoxicity
Trauma
Otologic Disease



Otosclerosis
Meniere’s Disease
Auditory Nerve
Tumors
Hearing Assessment
Main questions
1. Is hearing normal?
2. What is the degree
of hearing loss?
3. What type of
hearing loss is it?
Pure Tone Audiometry



Measurement of pure tone thresholds
between 250-8000 Hz
Air conduction
Bone conduction
Pure Tone Audiometry
The results of PTA tell us
1. Air conduction thresholds across
frequency tells us if hearing is normal or
not
2. If hearing by air conduction is NOT
normal, the thresholds tell us the degree
of hearing loss
Average Air Conduction
Threshold and the Degree of
Hearing Loss
Pure Tone Audiometry
The results of PTA tell us
1. Hearing by air conduction across frequency in
each ear tells us if hearing is normal or not
2. If hearing by air conduction is NOT normal, the
thresholds tell us the degree of hearing loss
3. Differences between hearing by air conduction
and hearing by bone conduction tell us the type
of hearing loss
Determining the Type of
Hearing Loss
Hearing Assessment
Speech Audiometry
Nonbehavioral
measures