ALDs and Acoustic Management

1
ALDs and Acoustic Management

• Presented by
• Lori Ausperk, M.S. CCC/A
• Educational Audiologist
• Mayfield City School District/Millridge Center
  for Hearing Impaired

2
Assistive Listening Devices (ALD)

• Assistive Listening Devices provide a direct
  channel from the speaker to the student.
• Their purpose is to help overcome adverse
  listening situations brought about by distance,
  noise and reverberation.

3
Types of ALDs

• FM- uses frequency modulated radio waves on
  protected channels to send a specifically tuned
  signal from the transmitter to the receiver
• Infrared (IR)- uses light beams to send a signal
  from the transmitter to the receiver

4
Pros and Cons of FM

• PROS
• Transmission range can extend up to 50 ft.
• Transmission can penetrate walls and ceiling
  within range.
• Consistent signal
• Miniature sizes available for ear level fittings.

• CONS
• Requires tuned frequency match with receiver
• Other technology like cell phones can interfere.
• For team teaching need two separate frequency
  bands.

5
Infrared (IR) Pros and Cons

• PROS
• Transmission cannot penetrate walls and ceilings
• No frequency match dilemmas.
• No interference issues with other technology.
• Team teaching possible with 2 microphones on 2
  different channels.

• CONS
• Transmission range is shorter
• Can have signal breaks caused by room
  barriers(hanging materials, corners, body and
  transmitter positions.
• Can have dead spots.

6
Forms of FM and IR

• FM
• Sound Field (Room)
• Personal (Desk Top)
• Ear level

• IR
• Sound Field (Room)
• Personal (Desk Top)

7
SOUND FIELD

• Teacher wears a wireless microphone. Her voice
  is picked up by a receiver and is amplified and
  played through speakers around the room.
• Can benefit ALL students not just hearing
  impaired.
• Classroom management is improved and discipline
  problems reduced.
• Better attention.
• Less vocal stress for the teacher.

8
Tips for Use

• Batteries
• Microphone placement
• Troubleshooting tips

9
Batteries

• Most systems use either a 9V or AA rechargeable
  battery.
• All rechargeable batteries are not created equal!
• Use Nickel-metal hydride (NiMh) battery.

10
Batteries (cont.)

• Charge the batteries overnight before first use.
• If you forget you can substitute a regular
  alkaline battery for the rechargeable.
• NEVER CHARGE AN ALKALINE BATTERY- it will leak or
  possibly explode severely damaging your
  equipment!
• Replace your rechargeable once a year.

11
Microphone Placement

• Head or boom microphones are most desirable in
  that they offer less chance for interference
• Lapel microphones should be placed 8 inches from
  the mouth.
• Be aware of clothing and jewelry that can rub
  against the mic and cause interference.

12
Troubleshooting (FM systems)

• Problem No Sound
• Make sure the frequency of the transmitter and
  receiver match.
• Verify that the receiver is on.
• Verify that the transmitter is on.
• Check connection between the receiver and wall
  outlet.
• Check that your batteries are charged and the
  polarity is correct.

13
Troubleshooting cont.

• Plug the receiver into a different wall outlet.
• Wiggle the microphone cord- if there is static or
  intermittency it should be replaced.
• Problem Weak or poor sound quality
• Recharge or replace batteries
• Check volume control settings on receiver box.
• Verify that the antenna is connected to the
  receiver.

14
Troubleshooting (cont.)

• Wiggle the microphone cord to check for static or
  intermittency.
• Check the speaker wires for damage.
• Check volume control on the receiver.

15
Troubleshooting (cont.)

• Problem Feedback
• Lower the volume control on the receiver.
• Increase the distance between the transmitter and
  the speakers.

16
Sound Field- Infrared

• Tips for batteries and microphone placement the
  same as those for the FM system.
• Make sure microphone is turned outward or light
  beam will not reach the receiver.
• If 2 mics are used in the classroom ensure they
  are on different channels.

17
Troubleshooting (Infrared)

• Problem No Sound
• Make sure transmitter and receiver are turned on.
• If 2 mics are being used ensure they are each on
  different channels.
• Make sure batteries are charged and polarity is
  correct.

18
Troubleshooting (cont.)

• Ensure that nothing is blocking the receiver.
• Make sure you see a green light on the receiver
  when speaking into the microphone.
• Try another teachers microphone in your classroom
  to see if it works.
• Ensure speakers are connected and power source in
  plugged in.
• Ensure that the transmitter is not on mute.

19
Desktop or Personal Amplification

• The teacher wears a transmitter.
• The student places the receiver on his/her desk.
• Both the transmitter and the receiver use
  batteries so both pieces must be charged each
  night.
• The student should have a designated spot for
  charging the equipment.

20
Ear Level FM

• Should only be fit by an audiologist
• Different implant processors require different
  hook ups.
• Consist of a transmitter and receiver.

21
Transmitter Options
22
Receiver Options
23
Acoustic Management

• Carpet
• Window treatments
• Covers on chair leg bottoms
• Minimize use of fans
• Keep the door closed