The Catholic University of America

 Assistive Listening Devices

Assistive Listening Devices (ALD’s) serve a variety of functions to help students hear better in multiple lifestyle situations. These devices are meant to be used either with or without hearing aids depending on the type. When used with hearing aids, assistive listening technology can increase the positive benefits associated with hearing aids and create a powerful combination.

Types of ALD’s

  •  FM Systems
  • Infrared Systems
  • Induction Loop Systems
  • One-to-One Communicators

What are ALD’s

ALD’s are devices that can help students with hearing loss function better in their  day-to-day communication situations. ALD’s  can be used with or without hearing aids or cochlear implants to make hearing easier—and thereby reduce stress and fatigue.

The following situations are difficult for all listeners, but they are especially difficult for people with hearing loss:

  • Distance between the listener and the sound source: The farther away you are from a speaker, of course, the harder it is to hear the speaker. This is because the intensity, or loudness, of a sound fades rapidly as it travels over distance. So, while you may have no difficulty hearing someone in close range, you may have considerable difficulty hearing the same person across the room.
  • Competing noise in the environment: Most rooms have background noise that competes with the spoken message or sound we want to hear. Examples of background noise include ventilation systems, others talking, paper shuffling, computers, radios, TVs, outside traffic or construction, and activities in adjacent rooms. Background noise can make hearing very challenging. For optimum hearing, speech should be at least 20–25 decibels (dB) louder than any competing noise. This is called the signal-to-noise ratio, or S/N ratio.
  • Poor room acoustics/reverberation: A room’s acoustics are the quality of sound maintained in the room, and they can affect your ability to hear effectively. Sound waves bounce off hard surfaces like windows, walls, and hard floors. This creates sound reflections and echoes (called “reverberation”). The result of excess reverberation is distorted speech. Large gyms, cathedrals, and open marble lobbies quickly come to mind when we think about reverberation. Reverberation also can occur in smaller spaces such as classrooms. We’ve all experienced how much easier it is to hear in rooms that are carpeted and have upholstered furniture (which absorbs noise) than in empty rooms with tile or cement floors.

Any one of these conditions (distance, noise, or reverberation) can create listening problems. More often than not, they occur together and have a debilitating effect on the ability to hear and process speech. ALD’s can help students overcome these listening difficulties.

DSS has two types of systems to loan.  One is a system that allows one student to hear the pers lecturing. the other system allows multiple people to hear the presenter or lecturer.  It is meant to be used in large audience situations.