Download Sensor neural Hearing Loss - O6U E

Therapeutic equipment I
Lecture (1)
What’s A Hearing Aid?
• Hearing aids are miniature electronic devices that sit in
or on the ear, and selectively amplify and process
sounds.
• All hearing aids contain one or more microphones to pick
up sound, an amplifier that amplifies and processes
sound, a receiver or speaker that sends the signal from
the amplifier into your ear, and a battery, or power
source.
• All of these components are packaged into various styles
to fit people’s cosmetic needs and power requirements.
Human ear
Hearing Loss
• There are three kinds of hearing loss:
–Sensor neural
–Conductive
–Mixed hearing loss
Sensor neural Hearing Loss
• Also known as nerve deafness, the inner
ear or actual hearing nerve itself is
damaged.
• About 90% of all people with hearing
impairments suffer from sensor neural
hearing loss.
• Most common.
Conductive Hearing Loss
• Outer and/or middle part of the ear fail to
work properly.
• Sounds become "blocked" and are not
carried all the way to the inner ear (where
hearing is still normal)
• Not permanent; temporary hearing loss
Mixed Hearing Loss
• A combination of a conductive and sensor
neural hearing loss.
• Both the middle and inner ear are
involved.
Causes of Conductive Hearing Loss
• a buildup of fluid in the middle ear.
• wax in the ear canal
• puncturing of the eardrum
• problems or injury to the bones or membrane
which carry sound from the external ear through
the middle ear to the inner ear.
Sensor neural Hearing Loss
• Usually permanent.
• not medically or surgically treatable.
• In most cases, the cillia or the nerves from the
inner ear to the brain are damaged.
• wearing hearing aids may be of significant
benefit.
Causes of Sensor neural
Hearing Loss
• The natural aging process.
• Exposure to loud noises.
• Infection or other disease.
• A genetic disorder
Treatment
• Sensor neural hearing loss is usually
permanent, no medically or surgically treatable.
• In most cases, the nerves from the inner ear to
the brain are damaged.
• However, most people with this hearing loss find
wearing hearing aids to be of significant benefit.
Identifying Hearing Loss
• Ranges have been established to help people
identify how much difficulty they should expect
from their hearing loss. The typical ranges for an
adult are:
• -10dB to 25dB = Normal range
• 26dB to 40 dB = Mild hearing loss
• 41 dB to 55 dB = Moderate hearing loss
• 56 dB to 70 dB = Moderately Severe hearing
loss
• 71 dB to 90 dB = Severe hearing loss
• over 90 dB = Profound hearing loss
Types of hearing aids
(1) Behind‐the‐ear
(BTE) aids:
–A
plastic
case
containing most parts;
resting behind the ear
connected to an ear
mold
– Easy to be cleaned
and handled.
(2) In‐the‐ear (ITE)
aids:
– All parts contained in a
shell, which fills in the
ear canal
– Relatively easier to
handle than smaller
aids such as ITC &
CIC
(3) In‐the‐canal (ITC)
aids & (4)
completely‐in‐the‐cana
l (CIC) aids:
– All parts contained in
tiny cases, which fits
partly or completely in
the ear canal
– Smallest in size, which
makes it difficult to
handle and adjust for
some users
Hearing Aids: Basic Components
Electronic components:
• Microphone
• Amplifier circuitry
• Miniature
loudspeaker/receiver
• Battery
Microphones
• Microphones are transducers that convert acoustical
energy into electrical energy.
• The three main types of microphones (according to
their principles of operation) are:
• Dynamic (moving-coil)
• Ribbon
• Condenser
Condenser microphones
• A capacitor is an electrical device able to store
electrical charge between two closely-spaced
conductors (plates).
• Capacitance (C) measures how much charge (Q) is
stored for a given voltage (V), such that C = Q/V
• Capacitance is inversely proportional to the distance
(d) between plates
• Condenser microphones generally have flatter
frequency responses than dynamic, and
therefore mean that a condenser microphone is
more desirable in the hearing aid.
• There are two types of condenser microphones;
standard condenser and electret condenser.
• A standard condenser microphone consists of a
small diaphragm that vibrates in response to
acoustic
pressure.
Standard
condenser
microphones have very high output impedance,
so they are not suitable for transferring signals
over even a very small distance.
Electret condenser microphone
• An
electret
condenser
microphone combines a
condenser microphone with
a Field Effect Transistor
(FET), which amplifies the
signal and transforms the
impedance to a more useful
level.
• This
characteristic
of
electret
condenser
microphones makes them
very sensitive to small
sounds.
• The electret condenser microphone
operating voltage is 3v, operating
frequency ranged from 20Hz to 20 KHz,
and operating temperature from -20c to
70c
Limitations
• Some problems in background noise.
• Can amplify loud sounds to the point
where they can be uncomfortable.
• Problems with manipulation. This is a big
problem for ITC and CIC aids.