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 CONS
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
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
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.
Wiggle the microphone cord to check for static or intermittency. Check the speaker wires for damage. Check volume control on the receiver.
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.
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.
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.
Acoustic Management Carpet Window treatments
Covers on chair leg bottoms Minimize use of fans Keep the door closed
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