ALDs and Acoustic Management

Presented by

Lori Ausperk, M.S. CCC/A

Educational Audiologist

Mayfield City School District/Millridge Center for Hearing Impaired

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.

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

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.

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.

Forms of FM and IR

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

• Ear level

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

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.

Tips for Use• Batteries

• Microphone placement

• Troubleshooting tips

Batteries• Most systems use either a 9V or AA

rechargeable battery.

• All rechargeable batteries are not created equal!

• Use Nickel-metal hydride (NiMh) battery.

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.

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.

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.

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.

Troubleshooting (cont.)

• Wiggle the microphone cord to check for static or intermittency.

• Check the speaker wires for damage.• Check volume control on the receiver.

Troubleshooting (cont.)

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

and the speakers.

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.

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.

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.

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.

Ear Level FM

• Should only be fit by an audiologist

• Different implant processors require different hook ups.

• Consist of a transmitter and receiver.

Transmitter Options

                                    

Receiver Options

                                                                                   

                          

                                  

Acoustic Management

• Carpet

• Window treatments

• Covers on chair leg bottoms

• Minimize use of fans

• Keep the door closed