Transcript Hearing_Loss

HEARING LOSS
Hearing Loss
• Children and Adults who
are deaf are those who
cannot hear or understand
conversational speech
under normal
circumstances. Their
hearing loss exceeds
75 db, and in many cases,
the loss may be greater
than 90 db.
THE HUMAN EAR
• The ear of an average,
healthy, young adult
can respond to
frequencies in the
range of 20 Hz to
20,000 Hz.
• The human ear is most
sensitive to sounds of
1000 to 4000 Hz.
Anatomy of the EAR
Anatomy of the Ear (Outer Ear)
• The Outer Ear (pinna),
captures sound waves
and funnels to the
middle ear.
• The tympanic
membrane is
commonly called the
eardrum.
Anatomy of the EAR (Middle Ear)
• The middle ear is that
part of the ear between
the external and the
inner ear. Its outer
border is the thin
membrane known as
the ear drum, or
tympanic membrane.
Anatomy of the Ear (Inner Ear)
• The inner ear is the
delicate structure which
transforms the sound
vibrations from the stapes
into nerve signals that are
transmitted to he brain.
• It also plays an important
role in maintaining our
balance.
Sounds
• Several animals can
hear sounds of much
higher frequency,
which is why humans
do not hear special
whistles that may be
heard by dogs.
• Sounds vary not only
in frequency, but also
in intensity.
Levels of Sounds
• For example, the
intensity of normal
conversational speech
varies between 50 and
70 db.
• Very intense sounds,
such as those of a
lawn mower, may be
as high as 100 db SPL.
Levels of Sounds
• The intensity of live
rock concerts may
reach 115 to 120 dB
SPL.
• A sound of 140 dB
induces pain.
Intensity
• Is related to amplitude,
which is the extent of
displacement of the
molecules in their
to-and-fro motion.
• The greater range of
displacement, the greater
the amplitude of sound.
• The greater the
amplitude of sound, the
higher the intensity of
sound.
Decibel
• The decibel is a
relative measure; it
helps compare the
intensity of one sound
against the other, a
standard.
• The decibel also is a
measure of sound
pressure.
PERMISSIBLE NOISE
EXPOSURE
PERMISSIBLE NOISE EXPOSURE
120
100
80
60
40
20
0
Duration of
exposure per day
(hr)
Noise Level (dba
Hearing Protection
• Noise Reduction
Rating - 29 dB
Hearing Protection
• Noise Reduction
Rating - 31 dB
Hearing Protection
• Noise Reduction
Rating - 22 dB
Hearing Protection
• Noise Reduction
Rating - 23 dB
A SELF HEARING EVALUATION
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Can you usually hear and
understand what a person says,
without seeing his face, if that
person whispers to you from across
a quiet room?
Can you usually hear and
understand what a person says
without seeing his face, if that
person talks in a normal voice to
you from across a quiet room?
Can you usually hear and
understand what a person says
without seeing his face, if that
person shouts to you from across a
quiet room?
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Can you usually hear and
understand a person, if that person
speaks loudly into your better ear?
Can you distinguish the sound of
speech from other sounds and
noises?
Can you usually tell one kind of
noise from another?
Can you only hear loud noises?
How difficult do you find it to
follow conversations if there is
surrounding noise (for instance,
while several people are talking at
the same time as in a restaurant?