What is an Assistive Listening Device?

Many individuals who use hearing aids effectively in quiet environments have a difficult time following information presented in large college classrooms. In the classroom, there is competing background noise, room echo, and distance from the speaker which can degrade the sound quality. Assistive listening devices (ALDs) are designed to improve the audibility of sound or a speaker by placing a microphone close to the sound source, so that it becomes louder compared to the other sounds in the environment. Assistive listening devices improve the ability to hear because they make the desired sound, i.e., a faraway voice (a professor in an auditorium), or a near sound that gets lost in other noise (listening to a peer converse in a group), stand out from the background noise.

ALDs can be used with hearing aids or cochlear implants (CIs), or can be used separately with a receiver and headphones. ALDs used in conjunction with hearing aids require a telecoil (T-switch). ALDs can also be used independently for individuals who do not have hearing aids.

What are the Different Types of Assistive Listening Devices?

ALDs utilize different technologies and can be wireless or wired. Wireless ALDs make use of radio frequencies, magnetic inductive energy, or light rays to transmit sound. Hardwired ALDs use direct electrical connection to transmit the auditory signal. Each system has special features, capabilities, advantages, and disadvantages.

Frequency Modulated (FM) System is a wireless, portable battery-operated device that uses radio transmission to send auditory signals, i.e. speech, from a transmitter to a receiver. FM systems are used in environments where there are multiple signals in close proximity and there is a need to separate the signals, i.e., multiple classrooms in a building. FM systems can receive a signal up to 200 ft.

Induction Loop Systems use electromagnetic waves for transmission. Sounds are picked up by the speaker's microphone, amplified, and sent through the wire/loop, creating an invisible electromagnetic field. The telecoil (T-switch) in the individual's hearing aid serves as a receiver for the signal. Induction Loop systems are used in facilities or buildings where there is only one signal, i.e., a church or theater, and do not require the use of a separate "add-on" device.

Infrared Sound Systems use multiple infrared light beams to send auditory signals from a transmitter to a receiver. Transmission of the signal depends upon the amount of light interference in a room, but can be stand-alone systems which can be moved from one area to another. Multiple systems can be used in adjacent classrooms without the need to separate the signals, because the infrared signal cannot be transmitted through solid classroom walls. However, signals can be transmitted through glass. 

What Types of Assistive Listening Devices are Available at MSU?

Michigan State University has over 310 classrooms with Frequency Modulated (FM) systems, which can be identified by signage in the classrooms. Students and employees in need of equipment may access receivers, teleloops, and headphones from the Resource Center for Persons with Disabilities (RCPD) at www.rcpd.msu.edu. Visitors using classroom spaces may access this equipment by contacting MSU Information Technology (MSU IT) by calling (517) 432-6200 or at tech.msu.edu.

MSU Wharton Performing Arts Center, which houses the Cobb Great Hall and the Pasant Theatre, has assistive listening resources. For more information, visit the Wharton Performing Arts Center website

MSU Breslin Event Center also has assistive listening resources. For more information, visit their website

How to Ensure Optimal Sound from an ALD

Classroom wireless microphones should be used in conjunction with the classroom FM systems. The wireless microphone should be worn three to five inches from the mouth for optimal sound projection. If a classroom FM system is not available, a personal ALD may be used. The personal ALD microphone should be worn three to five inches from the mouth.

When listening to audio from equipment sources (personal devices, DVD or Blu-ray player, etc.) in the classroom, ported from the technology carts, the wireless microphone can be powered off. Sound will be transmitted through the technology carts to the FM receiver.

When listening to audio from equipment sources (personal devices, DVD or Blu-ray player, etc.) in the classroom without a technology cart or classroom amplification system, the personal ALD should be placed three to five inches from the sound source. 

Questions asked or comments made by individuals not wearing the wireless microphone or personal ALD, need to be repeated by the individual or instructor wearing the microphone so the information can be heard by all individuals in the environment.

Problems with technology in the classroom; technology carts, wireless microphones, ALDs, captioning equipment, etc. can be reported to MSU IT by calling (517) 432-6200, or emailing ithelp@msu.edu. MSU IT offers immediate response to resolve technology issues in university classrooms and learning spaces.

Helpful Tips for Using the Assistive Listening Devices in MSU Classrooms


A picture of the ALD signage
ALD Signage

MSU classrooms with ALD signage indicate the presence of an FM system transmitter in the classroom. Use of a classroom wireless microphone is required to activate the features of the ALD. Ensure the needed equipment is powered on, and the volume is set to the optimal level.

A photo of an FM receiver
FM Receiver

An individual interested in accessing the classroom signal must have an FM receiver and headphones, or a teleloop if using the telecoil (t-coil) in a hearing aid.

The classroom signal includes audio from sources such as the host computer, personal devices, DVD or Blu-ray player and the wireless microphone.

MSU students and employees can obtain an FM receiver by contacting the Deaf/Hard-of-Hearing Specialist at the Resource Center for Persons with Disabilities (RCPD). Visitors may obtain FM receivers by contacting MSU Information Technology (MSU IT) at (517) 432-600, or by visiting tech.msu.edu. The classroom signal is accessed by turning on the FM receiver, selecting the ALD channel according to the channel number posted at the front of the classroom, and plugging the headset or teleloop into the headset jack on the FM receiver. Individuals using the FM teleloop need to turn-on the t-coil switch on their person hearing aids to access the sound coming from the headset jack on the receiver. Volume may be adjusted on the receiver for individual comfort and optimal sound.

In MSU classrooms without ALD signage, individuals may utilize personal ALDs which may or may not require the use of the classroom wireless microphone. The student or individual will provide a wireless transmitter/microphone to the instructor or speaker to be worn similar to a lapel microphone, and the student will wear the ALD receiver. Personal ALDs may be requested by students and employees from the Deaf/Hard-of-Hearing Specialist at the RCPD.