Assistive Listening Devices (ALDs)
When using infrared systems what must be maintained?
"Line of sight"
Wireless ALD Systems How do they work?
1) A wireless system picks up the audio signal, either through a microphone placed near the sound source or by means of a direct electrical plug-in 2) the sound is converted into an electrical signal by a transmitter and delivered through the air to a receiver worn by the user, often by means of radio waves or infrared (invisible light) 3) signal may be delivered to the ear either via earphones or through the individual's HA/CI
Alerting Systems When would you need an alerting device?
1) Can I hear the phone ring? 2) Can I hear if the doorbell rings or if someone knocks on the door? 3) Can I hear my alarm clock? 4) Can I hear the smoke detector? 5) Can I hear my baby cry or my spouse calling for me within the house?
How is the FM Receiver coupled to a HA/CI?
1) Direct Audio Input (DAI) 2) FM boot 3) Neckloop 4) HA with built in FM receiver
Hearing Aid Manufacturer Specific ALDs
1) Oticon Connectline (includes wireless cell, landline, and TV options - remote mic) 2) Phonak Com Pilot/ Com Pilot Plus and Remote Mic; Roger Pen 3) Signia (Siemens) Mini Tek System 4) Resound Remote Microphone w/ direct plug for iPods or MP3 players, with wireless TV and phone options as well
Examples of HAT
1) Vibrating/Flashing alarm clock 2) a doorbell signal coupled to a lamp, which flashes when the doorbell is rung 3) a smoke detector, where light flashes signal the presence of smoke 4) a baby cry alert system, where a parent can be signaled if a baby begins to cry in another room 5) a telephone ring signaler that causes a lamp to flash 6) text messaging with a cell phone and other text message display systems
Why ALDs?
1) audio signal could be presented at a distance, or in adverse listening conditions 2) HA/CI may not be enough to maximize listening potential in such situations
Sound field FM
1) beneficial for everyone in the class - Children without a HL, children with fluctuating CHL, and children with unilateral HL 2) does not require a student to wear a special FM receiver --> less hardware
Personal FM
1) better SNR than sound field system 2) receivers are required for everyone
Disadvantages of loop systems
1) can't assume everyone will have a T-coil 2) susceptible to electrical interference and spill over 3) must sit around looped area 4) may be dead areas within loop
Principles of ALDs
1) collect sound from the sound source and deliver it to the user's ear 2) Separate sounds you want to hear from background noise 3) Enable listener to hear when speaker is more than a few feet away
Advantages of infrared
1) compatibility: home receivers can be used with public transmitters 2) can be used in adjacent rooms 3) clear sound reproduction 4) appropriate for mild to moderate/severe loss 5) not affected by radio transmission
Wireless ALD Systems
1) do not use wire between microphone and the unit that delivers the signal to the user's ear
How and where is an induction loop used?
1) listener must sit inside/beside the loop 2) permanent loop systems in some theaters, classrooms, and religious settings
Advantages of Loop systems
1) low equipment costs 2) easy set-up and operation 3) induction receivers are compatible with ALL loop systems 4) unobtrusive with T-coil hearing aid
Disadvantages of FM
1) receivers are required for everyone 2) receivers vary in quality and durability 3) potential for outside interference 4) receivers and transmitters must be on the same channel 5) this system paid out of pocket is quite expensive
Disadvantages of infrared
1) receivers required for everyone 2) must have direct line of sight 3) indoor or evening use only 4) high intensity or fluorescent lights cause interference 5) large areas require multiple emitter panels 6) quality varies with company
FM Systems
1) resilient to noise and interference - it can help preserve the quality and clarity of transmitted sound 2) Use frequency bands which don't require a license 3) speech is frequency modulated onto a radio wave
General working of ALDs
1) speaker talks into a mic 2) transmitter sends signal across a distance 3) receiver to intercept the signal 4) sent to user's ear/HA/CI
In ALDs speech is sent ____ and avoids degrading effects of ____ and ____ on speech intelligibility
1) straight to ear 2) noise 3) distance
How does infrared system work?
1) transmitter/emitter sends the signal encoded in infrared light waves to a wireless receiver, which contains a photo detector diode 2) photo detector diode picks up the infrared signal and converts it back to the audio signal
Benefit of FM systems
1) very portable 2) very easy to set up and use 3) offers great flexibility of movement 4) used indoors or outdoors 5) appropriate for mild to profound losses 6) receiver can be covered or put in pocket 7) no fluctuation in strength of signal
How do induction loop systems work?
1) works by running a wire around the circumference of a room or table 2) sound picked up by microphone and converted to electric energy 3) wire conducts electrical energy from an amplifier and thus creates a magnetic field 4) induces the telecoil in HA to provide amplified sound to the user
Infrared Systems
Broadcasts from the sound source to a receiver/amplifier by means of infrared light waves Similar to FM systems, but use infrared waves instead of radio waves
In addition to ALDs
Closed captioning Rear Window Captioning Systems InSight Cinema
Ear Coupling
DAI, headphones, neckloop
What is reverberation?
Echoes caused by sound rebounding off surfaces such as walls, floors, and ceilings Rooms that have high ceilings, hardwood floors, and plaster walls tend to be highly reverberant, whereas those that have carpet and heavy draperies tend to have less reverberation
Wireless ALDs
FM, infrared, induction loop, simple amplification
Why may HA/CI not be enough to maximize listening potential in such situations?
Mic at level of ear and may not pick up sounds at a distance/may deliver sound and background noise
Roger Pen (Phonak)
Micro USB socket, Mic mode, connect, on-off, Bluetooth for smartphone connection
What is the Federal Communications Commission (FCC)?
Regulates FM systems, has allocated a range of bandwidths for exclusive use by persons with hearing loss (frequencies near 72 MHz and 216 MHz)
Examples of when wireless ALD systems may be used
Religious services, theaters, lecture halls
How is sound transmitted in wireless ALD Systems?
Sound is transmitted from the sound source to the individual by means of radio waves or infrared signals
Neckloop
Transducer worn around the neck, often as part of an FM assistive device system Consists of a cord from a receiver and transmits signals via magnetic induction to the telecoil of the user's HA
What is background noise?
Undesirable noise that masks the auditory signal of interest Example: in a classroom, the teacher's voice may be the target signal, and the rustling of paper and the shuffling of feet might be undesirable background noise
Classification of ALDs
Wireless, hardwired, HATs
Hardwired ALDs provide
a favorable signal-to-noise ratio to the user and, usually, an adjustable amount of signal amplification
Induction loop systems are portable
any room can be optimized
FM boot
bootlike device that houses an FM receiver, attaches to base of BTE HA/CI
InSight Cinema
brings captioned first run feature films to certain cities - captioning on the screen
FM Systems are most commonly used in
classrooms personal/sound-field FM systems
Hardwired Devices
devices that are directly connected by wires to sound source
Hearing Assistive Technology (HAT)
devices that facilitate reception of auditory information that is not speech, and auditory information by means other than amplification, such as by vibrotactile stimulation or visual display
Rear Window Captioning Systems
displays reversed captions on a light-emitting diode (LED) which is mounted in the rear of a theater Deaf and hard of hearing patrons use transparent acrylic panels attached to their seats to reflect the captions so that they appear superimposed on the moving screen
In Hardwired devices, the audio signal is converted into an
electrical signal
Where else can FM systems be used?
group lectures, religious services, theaters, one-on-one communication
DAI
hardwired connection that leads directly from the sound source to HA or other listening device
Infrared waves cannot be used with
high intensity/fluorescent light
Why are infrared systems not appropriate for outdoors?
sunlight interferes with infrared waves
Hearing assistive technology (HAT)
technology that facilitates access to auditory information
Telephone amplifiers amplify sound from a
telephone receiver
Simple amplification systems are most commonly implemented in
telephones
The electrical signal in hardwired devices travels through
the connecting wire, terminating at the user's hearing aid, headphones, or a neckloop
Why are hardwired ALDs not widely used?
they require the user to be tethered to the sound source
Infrared waves cannot travel through
walls
When and where are infrared systems used?
watching television, movie theaters
When are ALDs useful?
Ambient noise Reverberation Background noise
Simple Amplification Systems
Amplify the audio signal so that it is more audible to a person with hearing loss volume control
Hearing Assistive Technology (HAT) includes
ALDs
Sound Field FM System
Listening system, similar to the FM trainer, in which sound from a microphone is transmitted to loudspeakers that are positioned throughout the room
What is ambient noise?
Noise that is present in a room when it is unoccupied May emanate from open windows, air-handling, systems, computers, fluorescent lighting systems, or piped-in music
Personal FM Trainer
listening device in which speaker wears a wireless microphone and the speech is frequency modulated on radio waves transmitted through room to listener who wears a receiver
Hardwired ALDs are most often used for
listening to television, radio, or music
How do Hardwired devices work?
microphone may pick up the audio signal and deliver it to the patient's hearing aid by means of a DAI, or there may be a DAI jack that plugs into a piece of equipment, such as a television
Variation in induction loop systems
neckloop an induction loop wire system that can be worn around the neck
Simple amplification systems can be used by
normal hearing listeners
Induction loops are increasingly popular because
only T coil needs to be activated
What is frequency modulation (FM)?
process of creating a complex signal by means of sinusoidally varying a carrier wave frequency
