Chapter 7 Hearing Aids and Hearing Assistance Technologies.

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

BAHABone 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 AidsAnalog 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.

Programmable

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 ComponentsMicrophone 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

• HINT

• QuickSIN

• BKB-SIN

• SPIN

QuickSIN/BKB-SIN1.   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.

O v e r a l l R a t i n g f o r H e a r i n g A i d V e r y R a t h e r R a t h e r V e r y P o o r P o o r A c c e p t a b l e G o o d G o o d

0 1 2 3 4 5 6 7 8 9 1 0

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

• 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

R a t i n g f o r S p e e c h C l a r i t y V e r y R a t h e r R a t h e r V e r y P o o r P o o r A c c e p t a b l e G o o d G o o d

0 1 2 3 4 5 6 7 8 9 1 0

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:• 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.

Neckloop:• 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 Loop• Portable and able

to carry • Communicate one

on one or in small groups, cars, etc.

Loop Induction• LI transmits

via an electromagnetic 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 itself is the receiver)

• Loop receivers can be provided for people who do not have telecoils.

• Loops are often permanently installed

Neckloop

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 SystemsPhonak• 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 2.4-gigaHertz 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: TVTelevision • 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 intercomsphone 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