Transcript دكتر نيلفروش

IN THE NAME OF GOD
Fall 2013
M.H.Nilforoush
Audiology Department
School of Rehabilitation Sciences
Isfahan University of Medical Sciences
HUMAN SENSES
Seeing
Hearing
Taste
Touch
Smell
PEOPLE WITH HEARING LOSS
SUFFER EMOTIONAL, SOCIAL
AND COMMUNICATIVE
DYSFUNCTION
AGE OF HEARING LOSS ONSET
Group I: Mild Hearing Loss (15-30 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Unaided
2000
4000
8000
Group I: Mild Hearing Loss (15-30 dB)
Frequency in Hertz
125
250
500
1000
2000
0
20
40
Sound
level 60
in dBHL
80
100
120
Aided
4000
8000
Group II: Moderate Hearing Loss (30-60 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Unaided
2000
4000
8000
Group II: Moderate Hearing Loss (30-60 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Aided
2000
4000
8000
Group III: Severe Hearing Loss (60-90 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Unaided
2000
4000
8000
Group III: Severe Hearing Loss (60-90 dB)
Frequency in Hertz
125
250
500
1000
2000
4000
8000
0
20
40
Sound
level 60
in dBHL
Good auditory
resolution
80
Aided
100
120
Poor auditory
resolution
Group IV: Profound Hearing Loss (90-110 dB)
Frequency in Hertz
125
250
500
1000
2000
0
20
40
Sound
level 60
in dBHL
80
100
120
Unaided
4000
8000
Group IV: Profound Hearing Loss (90-110 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Aided
2000
4000
8000
Group V: Total Hearing Loss (>110 dB)
Frequency in Hertz
125
250
500
1000
2000
0
20
40
Sound
level 60
in dBHL
80
100
120
Unaided
4000
8000
Group V: Total Hearing Loss (>110 dB)
Frequency in Hertz
125
250
500
1000
0
20
40
Sound
level 60
in dBHL
80
100
120
Aided
2000
4000
8000
HISTORY
1551-Bone conduction device consisting of metal shaft or spear
1670- Sir Samual Moreland, England invented a large speaking trumpet
1892-first patent for electric hearing aid in the U.S.
1912-first volume control for a hearing aid
1931-first electric hearing aid eyeglass patent
1937-first wearable vacuum tube HA in US
1953-first all-transistor hearing aid
HA HISTORY
Ear trumpets
 Prehistoric
 Hollowed ram horns
 Speaking tubes (17th century)
 Direct sound from mouth
 Aurical Aids
 In-ear, around ear
 Limited frequency range
 Effective at less than 1000 Hz
Artificial ear drums (19th century)
 Perforated ear drum
 Try to insert rubber, cotton or dermal layer
 Wire attachment to ossicles
 Ineffective
EARLY ELECTRONIC HAS
Carbon-based (early 20th century)
 Carbon microphone
 Sound  Diaphram: moves carbon globules
 Motion of carbon in electric field creates current
 Gain 30 dB SPL
 Problems
 Static, no additional amplification
 Bulky, large battery
 Benefits
 Greater frequency range (500 – 2000 Hz)
Vacuum Tube (circa 1920)
 Multiple vacuum tubes response to current in microphone
 Problems
 Expensive, Multiple batteries, bulky
 Benefits
 Powerful (up to 140 dB SPL gain)
HISTORY OF HEARING AIDS
PARTS OF HEARING-AIDS
Block Diagram of the Hearing-Aid
Microphone
Amplifier
Receiver
PARTS OF HEARING-AIDS MICROPHONE
Microphone picks up soundwaves and converts them into electric signals
Microphone
Connections
Pre-amplifier
Wire / Electret Sheet (Live)
Membrane
Front Space
PARTS OF HEARING-AIDS
Function of the Microphone
Live Plate
Membrane
Air Space
Soundwaves
Transferral of > 10,000 Hz
Characteristics of Microphones:
•Very small design possible
•Hearing-aids normally contain 2 microphones (directional effect)
•Microphones are sensitive to moisture, HA sound is muffled by dirt
•In wind the microphones make noises (turbulence)
PARTS OF HEARING-AIDS - AMPLIFIERS
Amplifier amplifies the electrical signal coming from the microphone. The
modified signal is passed on to the receiver.
Characteristics of Amplifiers:
•The entire signal processing is integrated here (fully digital)
•Adaptation of the hearing-aid to hearing ability
•Documentation of the adaptation steps possible through NOAH
•At least 2 channels – high-frequency and low-frequency
•Restriction of output sound pressure level
PARTS OF HEARING-AIDS - RECEIVERS
Electrical signals are converted back into soundwaves in the receiver
Connections Coil Plastic Rivet Membrane
Magnet
Holder
PARTS OF HEARING-AIDS - RECEIVERS
Function of the Receiver
Transferral of up to 10,000
Hz
PARTS OF HEARING-AIDS - RECEIVERS
Characteristics of Receivers:
•Different sizes yield different performances – powerful receivers for powerful devices
•Large receivers do not have a high frequency range
(only up to approx. 6,000 Hz)
•Small receivers do not have high performance for e.g. musicians (CIC not good)
•There is usually hearing protection for the receiver (IE devices)
•Membrane can be destroyed in the case of operation at the performance limit
•Receivers can be destroyed by moisture (cerumen, sweat)
STRUCTURE OF A BEHIND-THE-EAR
HEARING-AID
Microphones
Ear Hook
Volume Adjuster
Amplifier
Receiver/Loudspeaker
Telephone Coil
Battery Contacts
Battery Drawer
Programme
Switch
Microphones
Connector
for
PC setting
Program switch
Sound in
Sound in
Loudspeaker
Telecoil
Signal processing
and amplifier
Off-Telecoil-Mic.
switch
Sound out
Battery
MANUFACTURER OPTIONS
FEATURES
Volume Control
Telecoil
Multiple Microphone Directionality
Compression
Clipping
Direct Audio Input
FM
Bluetooth
Programmability
Speech Enhancement/Noise Reduction
Frequency Shifting
Earmold/Vent
Remote Control
TECHNOLOGY
Analog: Settings and Sound are both processed via analog
technology.
Digital Programmable: Settings are processed digitally,
Sound is processed via analog technology.
Full Digital: Both Settings and Sound are processed
digitally.
Intelligent : All setting and sound are Processed intelligently
HEARING AIDS:
DESIRABLE CHARACTERISTICS
Speech Audibility
Physical comfort
“Audible” comfort
Not too much “background” noise
Not too loud
BTE (BEHIND-THE-EAR STYLE)
Attached to earmold
Powerful
Wide range of HL
Can have open earmolds
Less repair problems
Less feedback
Telecoils
ITE (IN-THE-EAR STYLE)
Fits in concha
Microphone at ear canal
level
Mild to severe HL
ITC (IN-THE-CANAL STYLE)
Only face sticks out into concha
Wide range of HL
Microphone at opening of ear canal
Takes advantage of most of the
auricle
CIC (COMPLETELY IN CANAL)
Hidden in canal
Full effect of auricle
Receiver very close to tympanic
membrane so requires less
amplification
Sometimes “extended wear”
RECEIVER IN THE CANAL (RIC)
Bone Hearing Aid
Eye Glass Hearing Aid
Hearing loss + low vision
Bone Hearing Aid
• Microtia
• Allergy to ear mold
• Recurrent chronic OME
Implantable Hearing Aid
BAHA
TYPICAL AUDIOGRAMS
Unilateral Conductive
Hearing Loss
• Fitting on none hearing
side means
• Stereophonic hearing
can be re-established
:-Snik AF et al, Nijmegen
®
Need for bilateral Baha
•
Transcranial attenuation 515dB (Stenfelt etal, 2000)
•
Improved Directivity index
•
(Van der Pouw, 1998)
•
Binaural summation 3 – 6dB
•
Improved speech reception
–
•
(Hamann et al 1991)
Improved speech in noise
–
(Bosman et al,2001)
Paediatrics
SOFT BAND
• For babies too young for surgery
(<3 years)
• Can be fitted from 3 months
• Can be placed at different
positions therefore reduces
pressure to one part of head
• Simple to fit and adjust
• Bilateral attachment for
directionality ??
• Available in several colours
• Less effective contact than screw
fixture
The result when surgery is performed well
VIBRANT SOUND BRIDGE
Audio Pro.
Full Implantable Hearing Aid
A totally implantable hearing system
that is implanted under the skin
behind the ear and within the middle
ear space
Has no microphone
 Uses the functioning eardrum to pick up
vibrations
 Adjusts vibrations to individual hearing
needs
Pacemaker like battery
 Needs replacement after 3 to 5 years of
continuous use.
 battery replaced in a minor outpatient
surgical operation.
WHAT IS ESTEEM?
ESTEEM IMPLANT USES
NATURAL ANATOMY
Sound Processor
Installed in recess of mastoid bone
Driver
Delivers increased energy
to stapes
Sensor
Senses vibrations
from incus
TODAY’S HEARING AIDS: SPECIAL
FEATURES
Directional Microphones
Noise Reduction Algorithms
Multiple Listening “Programs”
Automatic adjustments
Feedback controls
Bluetooth/wireless compatibility
Left-Right Communications
…
“BEST” HEARING AID
Degree/Configuration of loss
Individual Listening Needs
Cosmetics/Style
Ability to Manipulate Small Objects
“Gadget” Tolerance
Cost
3. HOW DO THE AIDS AFFECT YOUR TINNITUS?
McNeill, C. 2005
FM
• Educational Setting
• Increasing SNR
Negative factors for speech understanding:
Noise
Distance
Reverberation
What’s the solution?
r
Who is candidate?
 At least Moderate to Severe hearing loss
 Having problem in situations which FM can help
 Motivated to use an accessory
Which Transmitter?
Which Receiver?
WHY SHOULD I WEAR A HEARING AID ON BOTH
EARS?
1. Preserve Ear
2. Better Hearing in Noise
3. Localization
QUESTIONS
THE BETTER HEARING, THE BETTER LIFE
THANKS FOR YOUR ATTENTION