Assistive Listening Devices and Sound Field System

Assistive listening systems, also known as assistive listening devices (ALD), transmit sound directly to an individual who is wearing a sound receiver (hearing aid, headphone, neck loop etc.). ALDs reduce problems associated with background noise in one-on-one and group communication. By sending the sound signal directly to the individual's ears, an ALD enables the individual to hear and understand important sounds while also reducing frustration associated with hearing unwanted background noises.

There are three major types of ALD technology: FM radio signal, infrared light, and induction loop systems. FM systems transmit sound via radio waves. FM broadcast frequencies (72-76 MHz) are designated for use by FM systems. Infrared systems use lightwaves to send electrical signals to receivers that convert the electrical signals back to electrical energy and then sound. Induction loops use electromagnetic transmission to send sound through a loop of wire surrounding a seating area. A personal amplified system is another ALD option for one-on-one conversations and home media purposes. The personal systems are very small and portable and involve the use of a small microphone and receiver.

ALDs can be used to accommodate applicants or employees who are hard of hearing and who benefit from amplification. ALDs can be used for one-on-one communication with coworkers or clients, small group meetings and training situations, or large-area listening situations, such as conferences or social events.