GROUP AMPLIFICATION SYSTEMS

Back to the Aural Rehabilitation Class Page

I. Rationale

This results in a poor ________ ratio....

i.e. the intensity of the ________ at the listener’s ear is greater than the ________ of the speaker.

the ________ is 10 dB more intense than the ________

the ________ is 20 dB more intense than the ________

So...ideally we want to have a ________ S/N ratio and a constant signal level regardless of distance

This arrangement is known as an

Assistive ________ Device

Induction Loop

________

FM System

A. Induction Loop Amplification (ILA)

1. As current passes through a ________ of wire, an electromagnetic field is created and a signal can be received via ________ on HA or via a t-coil adapter

2. Advantages of ILA

a. mobility within a range around the loop

b. doesn't require a special ________, i.e.-many aids have t-coils

c. relatively ________

d. easy to install

3. Disadvantage of ILA

a. can get ________ from an adjacent loop

b. tend to be noisy

c. lose ________ frequencies

d. signal varies with position of the t-coil

e. speaker generally wired to amplifier

B. Infrared System

1. The signal from the ________ is transmitted via infrared________ which are picked up by a specialized receiver.

2. Advantages of Infrared

a. high ________ signal

b. mobility as long as there's no obstruction of the ________ signal

c. consistent signal

3. Disadvantages of Infrared

a. expensive

b. difficult to ________

c. some interference with ________

d. used primarily in fine arts audio or for home T.V. watching

C. FM System

1. Signal from the speaker is transmitted via ________ to a receiver which decodes it. The transmitter & receiver must be on the same channel.

2. Advantages of FM Systems

a. complete ________

b. simple to install

c. many options for ________

3. Disadvantages of FM Systems

a. may get interference from ________ or stray FM signals

b. need to match ________

A. Microphones for the Speaker

B. Transmitters

C. Receivers for the Listener

D. ________ to the Listener’s ear

E. Batteries

F. Chargers

1. Internal

2. ________

3. Boom

4. Conference

Mics can be omnidirectional or directional

1. Transmitting Frequencies

72 MHz to 80 MHz or

216 MHz to 217 MHz

Narrow Band (________ Channels)

Wide Band (10 Channels)

2. Fixed or ________ Trans. Frequency

3. Options: input jack, lights, volume

1. 3 styles: Body, BTE, Boot

2. Fixed or Variable Frequency

3. Signal Options (FM, ________, ENV)

4. Options for inputs, lights, volume controls (FM and ENV separate or together)

1. Button Receiver-must remove personal HA

2. Silhouette-wafer next to HA- use T switch

3. Neckloop - use it with HA set toT switch

4. Direct Input-electrical connection into the HA (switches vary across manufacturers)

5. Headphones-for normal hearing or mild loss

6. Soundfield Speakers

1. Most are Nickel-Cadmium-rechargeable

2. Some use ________ (9 volt or 2 AA)

3. BTE /Boot receivers use regular HA battery

1. Case Chargers-several units at once

2. ________ Chargers-add as you go

3. Wall Chargers-plug into devices

1. proper distance________

2. don't stand near noise

3. turn off when leave room

4. ________ must hang free

1. clean units with damp cloth

2. if put in prolonged storage-need even ________

3. annual electroacoustic checks

4. daily________ checks

Set Receiver to pickup ________ Only Signal

Set Receiver to pickup ________ (ENV) Signals

Set Receiver to pickup up ________ Signals

Set Receiver to pickup ________ Signals

D. Trouble shooting - works best when two people check each ________ separately and add progressively

1. check FM receiver in ________ mode (body aid)

2. check FM receiver & transmitter in FM mode

3. check FM receiver & transmitter in FM & ENV mode

4.     check FM Receiver & transmitter & personal aid (boot with ________ silhouette)

5. check personal aid alone.

6. annually check each component, daily check ________ system (#4)

1. setting volume controls - must be determined by audiologist

2. matching crystals/________

3. setting the mic switch

4. neckloops often ________ & inconsistent signal

5. changes in frequency response re: to hearing aid alone when using direct input or neckloop

6. access to ________ who can monitor

7.  dead batteries

8.  broken cords

1. Phonic Ear Body worn system- $1300 for T & R

2. Telex Body worn system- $1300 for T & R

3. Comtek  Body worn system- $________ for T & R

4. BTE Receivers (Telex, Sonnovation, Phonic Ear $1500)

Some School Districts will purchase FM

Some State Hearing Aid ________ Programs

Some Rehab Agencies- Texas Rehab Commission

Service Organizations

Back to the Aural Rehabilitation Class Page