ALD Primer Document

Presented by Jay Thurman; B.Sc., BC-HIS
Communication Consultant

Assistive listening devices are any group of products that are specifically designed to improve the signal to noise ratio of the listener.  This is accomplished by picking up the desired sound from as close to the sound source as possible and sending it directly to the listener's ear.  In this way, the integrity of the speech signal is maintained regardless of the environmental conditions, such as noise, reverberation or distance from the speaker.  ALD's can be used alone or in conjunction with personal hearing instruments.  They can be coupled with headphones, earbuds, neckloops, or direct audio input.  Care must taken that the volume level is appropriate to the hearing loss or processing problem.

Assistive listening devices cover a wide range of products from personal amplifiers and television listening devices to large area and stadium size systems for the hearing impaired.  This paper will cover the assistive devices we refer to as Wide-Area Assistive Listening Devices or systems.  This group of devices are designed to assist people with hearing impairments hear what is being said at everything from small meetings and round table discussions to major theatrical and sporting events held in the largest of facilities. 

Wide area assistive systems generally fall into one of three categories.  These categories are Induction loop systems, F.M. (Frequency Modulated) systems, and Infrared systems.  Each system has its advantages and disadvantages which this paper will attempt to point out and clarify. 

Continue