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Chapter 7
Hearing Aids
and
Hearing Assistance Technologies
Purpose of Listening Devices
• Make speech audible
• Make non-speech audible
• Restore range of loudness
Hearing Challenges
•
•
•
•
Hearing soft speech
Hearing speech clearly
Hearing speech in noisy environment
Hearing speech in reverberant environment
Definition of Hearing Aid
• Hearing Aids (noun, plural)
1 (archaic): electronic devices usually worn by a
person for amplifying sound before it reaches the
auditory receptor organs.
2 (modern): electronic devices worn by a person
for processing sound to provide audibility and
improve the signal-to-noise ratio before it reaches
the auditory receptor organs.
A New Definition for Modern Hearing Aids, Victor Bray, Ph.D. & Michael Nilsson,
Ph.D., Auditory Research Department, Sonic Innovations, Inc.
Types of Listening Devices
•
•
•
•
•
•
Hearing Aids
ALDs/HAT
Alerting Devices
Brainstem Implants
Bone Anchored Hearing Aids (BAHA)
Cochlear Implants (CI)
Hearing Aid Styles
• Air conduction
– Body Aid
– Glasses
– BTE
• RITE
• RITA
– ITE
– ITC
– CIC
• Bone Conduction
• Bone Anchored (BAHA) (above 20
years) (now considered a mastoid
implant)
Open Canal
• Receiver in the Ear
– RITE
• Receiver in the Aid
– RITA
Bone conduction HA
• When a conventional
hearing aid cannot be
worn due to
microtia, atresia,
obstruction in EAM,
bone conduction
hearing aids may be
beneficial
BAHA
Bone Anchored Hearing Aid:
• Surgically embedded titanium "post"
into skull with a small abutment
• A sound processor sits on abutment
• The implant vibrates the skull and
stimulates the cochlea via bone
conduction bypassing outer &
middle ear
• Treatment for:
– Conductive loss
– Mixed hearing losses
– Unilateral sensorineural hearing
loss,
– Chronic ear infections
– Congenital external auditory
canal atresia
Hearing Aids
• Analog (conventional)
• Programmable (analog or digital)
• Digital
Type of Hearing Aids
Analog
hearing aids pick up the sound and convert it into electronic signals.
These hearing aids have trimmers that are manually adjusted by a
hearing healthcare professional using a tiny screwdriver. Analog hearing
aids are the least flexible, but also the least expensive, level of hearing
aid technology.
Progra
mmable
Programmable hearing aids must be connected to a computer in order
for your hearing healthcare professional to make adjustments. These
hearing aids offer more flexibility and can provide more features.
Digital
Digital hearing aids contain computer chips that convert the electronic
signal into digital signals. The digital hearing aid can perform complex
processing of the sound, such as reducing the intensity of loud
background noise. Typically programmed via a computer, offers the
greatest flexibility in its ability to match the hearing aid response to the
hearing loss.
HA Components
Microphone
The microphone picks up sounds from the air
and convert them into electrical signals.
Amplifier
The amplifier increases the intensity of the
signals from the microphone. Filters modify the
sounds so that only sounds which are relevant
for the person are amplified.
'Loudspeaker' (Receiver)
The third basic component is the 'loudspeaker'
(receiver). It converts electrical signals into
acoustic signals, which the person then hears.
Small computer (Digital) (How it works)
These three components exist in all hearing
aids. Furthermore, in digital hearing aids a small
computer can be programmed to manipulate the
signals to fit the hearing loss of the individual
hearing-impaired person.
Batteries
• Various Sizes
• Chemical
Earmolds
• Earmolds direct
sound into the ear
canal
• Variety of styles,
colors, and other
characteristics
Verification of HA
• Real Ear (probe microphone)
• Speech tests (HINT, QuickSIN, BKB-SIN,
SPIN)
• Subjective ratings of intelligibility and
quality
• Loudness verification
• Questionnaires
• Functional gain
• ABR—for infants & young children
Probe Microphone
• Real Ear
measures of
sound
pressure in
the ear canal
Speech Tests
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•
•
•
HINT
QuickSIN
BKB-SIN
SPIN
QuickSIN/BKB-SIN
1. SNR loss of 0-2 dB: Normal to near-normal.
These patients will probably do well in noise with any hearing aids that
provide undistorted output. With directional microphones, they may hear
better than their normal-hearing peers in noisy situations.
2. SNR loss of 2-7 dB: Mild SNR loss.
Today’s directional microphones provide SNR improvements of 2 to 5 dB;
with directional microphones, these patients should be able to hear almost
as well as their normal-hearing counterparts in noisy situations.
3. SNR loss of 7-15 dB: Moderate SNR loss.
While directional microphones will provide benefit for these patients, they
cannot provide enough SNR improvement to allow the person to hear as
well as their normal-hearing counterparts in noisy situations. Microphone
arrays, such as the LinkiT, provide a 7 to 13 dB improvement in SNR.
4. SNR loss greater than 15 dB: Severe SNR loss.
These patients need the maximum amount of SNR improvement, and FM
systems are the technology of choice for these patients. Today’s ear-level
FM systems are cosmetically appealing and are available in a wide range of
hearing aids. Contact hearing aid manufacturers for more information.
Subjective Ratings
• Magnitude Production
– Pt is given a number and instructed to
adjust a given parameter such as
intensity, SNR, until that number is
reached
Overall Rating for Hearing Aid
Very
Poor
• Category Scaling
– Pt is given a bounded scale such as 1 to
10 and asked to make a judgment of a
speech passage based on intelligibility,
quality, etc.
• Paired Comparisons
– Pt compares 2 different settings or
hearing aids
• Clarity
– Pt asked to judge if sound is clear,
distinct, pure…the opposite is diffuse
0
1
Rather
Poor
2
3
Rather
Good
Acceptable
4
5
6
7
Very
Good
8
9
10
Rating for Speech Clarity
Very
Poor
0
1
Rather
Poor
2
3
Rather
Good
Acceptable
4
5
6
7
Very
Good
8
9
10
Loudness Restoration
• PAL
• Soft, comfortable, loud
Functional Gain
• Compare Aided vs.
Unaided results
• In the example, the
aided (green)
thresholds are
compared to the
unaided thresholds for
the right (red) and left
(blue) thresholds
Questionnaires
• APHAB
• PAL
Binaural vs. Monaural Advantage
•
•
•
•
head shadow
loudness summation
localizing
signal to noise ratio
ALDs/HAT
ALDS/HAT
• Loop Induction (Loop)(Electromagnetic)
• Radio Frequency
–
–
–
–
AM
FM
FM plus Video
BlueTooth
• Light (Infrared)
ALDs/HAT
Loop Induction Systems
Looping the World with Audiocoil
• “The ordinary telecoil is perhaps the most
common and most underestimated assistive
listening device available for hearing impaired
individuals today.”
– Ross (2002).
• “By changing the label to something more
general—my suggestion is ‘audiocoil’—we do
not restrict to a single function the way we
think of the coil”.
– Ross (2006). Telecoils are about more than
telephones. The Hearing Journal, 59, 24-28.
LI Components
•
•
•
•
Microphone
Loop amplifier
Loop wire
Telecoil
Loop Inducton
• Large area
• Home area
(cushion loop
pad)
Loop Options
Silhouette:
Neckloop:
Portable Loop
• Near telecoil and
signal relatively low
therefore less
susceptible to) most
EMI
(ElectroMagnetic
Interference).
• Stay aligned relative
to the hearing aid,
they are less
sensitive to head
position.
• Drive both hearing
aids (not with true
stereo, but with a
mono signal into
both aids).
• Does not require
wires running up the
neck to the hearing
aid(s), and can be
worn under a shirt
or jacket.
• Portable and able
to carry
• Communicate one
on one or in small
groups, cars, etc.
Loop Induction
• LI transmits
via an
electromagn
etic field and
require no
receiver if
the hearing
aid wearer
has a telecoil
• Oval
Window
Loop Induction: Telecoils
• Inductive/audio loop
systems transmit an
electro- magnetic field
• Receivers are not necessary
for hearing aid wearers
with a telecoil (the telecoil Neckloop
itself is the receiver)
• Loop receivers can be
provided for people who do
not have telecoils.
• Loops are often
permanently installed
Direct audio
input
Silhouette
inductor
ALDs/Hat
Radio Frequency
Systems
Radio Frequency
• FM (radio frequency) systems transmit radio
waves to receivers
• Used in classrooms and where mobility is required
• Not affected by light, able to cover 100+ feet, and
are portable
• Systems can be set to different frequencies to
allow several uses in same place
• Miniaturized FM receivers using the 216-217 mhz
range are available as an attachment for some
BTEs and CI processors
• Some FM transmitters have built-in microphones
that can switch from an omnidirectional,
directional and/or super directional setting
• Susceptible to some radio interference
Radio Frequency Systems
Phonak
• Multi-frequency receivers (MLxS, ML8S and ML9S)
synchronized automatically using the WallPilot or directly with Campus S. The MLxS
also has a standardized connector that makes it compatible with both Phonak hearing
instruments and BTEs from other manufacturers
• Single-frequency receivers (MLx, ML8, ML3-7)
– single-frequency receiver which clips to BTE hearing aid
• MicroLink CI S
– miniaturized FM receiver for cochlear implant users that attaches directly to the
bodyworn speech processor
• WallPilot
– hangs at the entrance to a room and performs an Automatic Frequency
Synchronization (AFS) and ensures that the multi-frequency receivers of wearers
entering the room are automatically set to the correct frequency
Phonak iLink
Phonak SmartLink
FM Radio Frequency Systems
Phonic Ear
• Sprite BTE FM
– used by people of all ages who have
hearing abilities ranging from
normal to profound loss used in the
car, at restaurants and parties,
watching TV, on tours, and talking
with others across a distance.
– students with ADD or CAPD
benefit
• Toteable
Oticon
AVR
BlueTooth
• Bluetooth is a short-range, wireless, digital
communication standard.
• Bluetooth devices send data and voice in a
clean, clear, digital format
– audio signal is not subject to the same sources
of signal degradation that sometimes
compromise the quality of analog (FM, AM or
inductive) transmissions.
• Radio frequency transmission in the 2.4gigaHertz range
BlueTooth Advantages
• Bluetooth signal is extracted from the noise; it
alone is transmitted and amplified, while noise is
rejected.
• Minimizes battery consumption for portable
devices
• Also, it places an intentional limit on the range of
transmission — the most common version has a
range of 10 meters which helps to avoid
interference among nearby devices
• Walls and other obstacles have a negligible effect
on Bluetooth transmission
BlueTooth Interference Advantage
Starkey
ELI
ALDs/HAT
Infrared Systems
Infrared
• Infrared systems transmit sound via
infrared light waves to receivers worn
by users
• IR commonly used in courtrooms,
movies, and live performance theaters,
conventions and with TVs (signal
contained in room)
• Infrared systems may be susceptible to
interference from bright sunlight or
fluorescent lights
• Requires line-of-sight between the IR
transmitter and the receiver, IR waves
can effectively reflect off some
surfaces, depending upon the power of
the transmitter
Audiovisual FM
• AudiSee
– Assistive device to facilitate speechreading and hearing, primarily
in educational settings
– Portable
– Camera and microphone worn by speaker
– less strain to speechread when teacher moves about the classroom
or turns to write on the blackboard
Sound Field Systems
• Portable or permanently
installed speakers placed close
to listeners at a distance from
the speaker
• They are most often used in
classrooms and are helpful for
people with mild to moderate
loss
• They offer a secondary benefit
to those who are not HOH
• Wireless speakers perform the
same function.
– Audio Enhancement Video 1
– Audio Enhancement Video 2
Vibrotactile Devices
Tactaid - small,
battery-powered
instruments that
can help a deaf
person understand
sounds by
allowing the user
to feel the unique
pattern of
vibrations present
in every sound
Hearing assistive technology (HAT)
• refers to devices and services that help
deaf and hard of hearing people
compensate for their hearing loss
• four primary categories of technology:
–
–
–
–
assistive listening devices
alerting devices
telecommunications devices
visual communication devices
ALDs/HAT Function
• Catch the desired sound as cleanly as possibly
– (using well-selected microphones or a direct audio feed)
• Carry the sound intact via a specific type of transmission
to a receiver
– (using infrared light waves, radio waves, induction, or wires)
• Couple the receiver to the hearing device or ear with as
little background noise, feedback or distortion as possible
– (using neckloops, silhouettes, cords, headphones, or earbuds,
depending on the user's equipment or lack thereof).
How ALDs/HAT Help
• Bypassing or minimizing background noise
• Overcoming the weakening effect of sound
traveling through air
• Reducing the effect of poor room acoustics
ALDs (HAT)
• assistive listening devices and systems (including couplers and
accessories for hearing aids and cochlear implants)
• alerting devices and systems (weather, doorbell, phone,
fire/smoke alerting devices)
• amplified telephones (some of which have tone controls and/or
audio output jacks) and telephone accessories
• TTYs (teletypewriters), VCO (Voice Carry Over) phones,
CapTel, and telecommunications-related software and services
• speech-to-text services and technology, such as CART
(Computer Assisted Realtime Transcription), C-Print and CAN;
closed caption decoders
• videophones and other visual technology to facilitate
speechreading and/or the use of sign language or cued speech
TELECOMMUNICATIONS
• Television
• Telephones
– POTS
– Cell Phones
TELECOMMUNICATIONS: TV
Television
• There are two ways to understand communication on
TV: hear it or read it:
– closed captions, a menu option ability built into most TVs
(TVs over 13 inches in diameter sold after 1993).
• ALDs
– Increase volume on a personal receiver, not TV sound
across the room
– Most are cordless and utilize different types of technologies
– Some devices marketed specifically for TV use
– Hearing aid users and non hearing aid users can use
technologies
TELECOMMUNICATIONS:
PHONES
• Two needs with phones:
– understanding conversation on the
phone
– knowing phone is ringing
• There are two ways to understand the
conversation on the phone: hear it or
read it. There are four basic types of
telephone amplifiers: portable,
handset, inline and phone set.
TELECOMMUNICATIONS:
PHONES
Types of telephone amplifiers:
• Portable
• Handset
• Inline
• phone set
TELECOMMUNICATIONS:
PHONES
Portable amplifiers
• Not recommended for regular use
• Inconvenient--strapped onto a phone
handset and need to be turned off after
use or the battery runs dead
• Occasionally helpful with wireless
phones that do not have amplification
• May make a phone hearing aid
compatible
• Peace of mind for use while traveling
TELECOMMUNICATIONS:
PHONES
In-line amplifiers
• devices that connect to the jack
in the phone where the curly
handset cord plugs in
• may be a good value, as some
go as high as 40 dB
• Compatible with most phones,
home and business.
TELECOMMUNICATIONS:
PHONES
Amplification handsets
• Replace original phone receiver
• Less popular
• Adjustment controls in the handle
• In some cases, not electrically
compatible
– universal amplifier (battery or A/C
powered) used for compatibility
TELECOMMUNICATIONS:
PHONES
Amplified phones
• Many features
• Some provide 50 dB gain.
• Louder not always helpful for clarity
• Some provide tone control
• Additional features (optional)
–
–
–
–
–
–
variable ringer sounds
built-in ringer light flash
big buttons for dialing
audio jack HAT
may require electrical outlet connection
cordless amplified phones
TELECOMMUNICATIONS:
PHONES
• TTYs do NOT use voice recognition
• TTYs are data terminals that allow hard of hearing or deaf people to
read typed messages
• Some TTYs have a keyboard for typing a response
• helpful to consumers who do not have clear speech
• majority of hard of hearing prefer to voice their response.
• Therefore styles of TTYs that are designed specifically to support VCO
(voice carry over) may be appealing
• One portable version is the size of a deck of cards and can be strapped
onto most phone receivers.
• TTY users communicating directly with another TTY or a relay
service used to type spoken message to TTY user
• VCO users find very appealing as they can read & talk and not worry
about missing hearing message
• With VCO, the TTY is then used for reading only.
• With computer, it is possible to purchase software to emulate TTY
signals
TELECOMMUNICATIONS:
PHONES
Other telecommunications devices
• pagers,
• cellular phones,
• fax machines,
• email and
• Internet chatting, and
• text-based intercoms
phone company custom calling helpful features
• caller ID (for calling back the person through relay
• distinctive ringing (for differentiating voice and TTY calls)
• voice mail (to listen to voice messages with amplified
phones or via the relay service)
Hearing Aids and You!
Cochlear Implants
• Medel
• Advance Bionics
• Cochlear