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Assistive Listening Devices (ALD)

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Introduction

Assistive listening devices (ALDs) help amplify the sounds you want to hear, especially where there’s a lot of background noise. ALDs can be used with a hearing aid or cochlear implant to help a wearer hear certain sounds better.

Types of assistive listening devices

Several types of ALDs are available to improve sound transmission for people with hearing loss. Some are designed for large facilities such as classrooms, theaters, places of worship, and airports. Other types are intended for personal use in small settings and for one-on-one conversations. All can be used with or without hearing aids or a cochlear implant. ALD systems for large facilities include hearing loop systems, frequency-modulated (FM) systems, and infrared systems.

Hearing loop (or induction loop) systems use electromagnetic energy to transmit sound. A hearing loop system involves four parts:

  • A sound source, such as a public address system, microphone, or home TV or telephone
  • An amplifier
  • A thin loop of wire that encircles a room or branches out beneath carpeting
  • A receiver worn in the ears or as a headset

Amplified sound travels through the loop and creates an electromagnetic field that is picked up directly by a hearing loop receiver or a telecoil (see sidebar), a miniature wireless receiver that is built into many hearing aids and cochlear implants. To pick up the signal, a listener must be wearing the receiver and be within or near the loop. Because the sound is picked up directly by the receiver, the sound is much clearer, without as much of the competing background noise associated with many listening environments. Some loop systems are portable, making it possible for people with hearing loss to improve their listening environments, as needed, as they proceed with their daily activities. A hearing loop can be connected to a public address system, a television, or any other audio source. For those who don’t have hearing aids with embedded telecoils, portable loop receivers are also available.

What’s a telecoil?

A telecoil, also called a t-coil, is a coil of wire that is installed inside many hearing aids and cochlear implants to act as a miniature wireless receiver. It was originally designed to make sounds clearer to a listener over the telephone. It also is used with a variety of other assistive listening devices, such as hearing loop (or induction loop) systems, FM systems, infrared systems, and personal amplifiers.

The telecoil works by receiving an electromagnetic signal from the hearing loop and then turning it back into sound within the hearing aid or cochlear implant. This process eliminates much of the distracting background noise and delivers sound customized for one’s own need. For people who are hard-of-hearing who do not have a telecoil-equipped hearing aid or cochlear implant, loop receivers with headsets can provide similar benefits but without the customized or “corrected sound” feature that matches one’s hearing loss pattern.

Many cochlear implants have a telecoil built into the sound processor, or can use an external telecoil accessory with both hearing aid compatible telephones and public loop systems. A simple switch or programming maneuver performed by the user activates this function.

FM systems use radio signals to transmit amplified sounds. They are often used in classrooms, where the instructor wears a small microphone connected to a transmitter and the student wears the receiver, which is tuned to a specific frequency, or channel. People who have a telecoil inside their hearing aid or cochlear implant may also wear a wire around the neck (called a neckloop) or behind their aid or implant (called a silhouette inductor) to convert the signal into magnetic signals that can be picked up directly by the telecoil. FM systems can transmit signals up to 300 feet and are able to be used in many public places. However, because radio signals are able to penetrate walls, listeners in one room may need to listen to a different channel than those in another room to avoid receiving mixed signals. Personal FM systems operate in the same way as larger scale systems and can be used to help people with hearing loss to follow one-on-one conversations.

Infrared systems use infrared light to transmit sound. A transmitter converts sound into a light signal and beams it to a receiver that is worn by a listener. The receiver decodes the infrared signal back to sound. As with FM systems, people whose hearing aids or cochlear implants have a telecoil may also wear a neckloop or silhouette inductor to convert the infrared signal into a magnetic signal, which can be picked up through their telecoil. Unlike induction loop or FM systems, the infrared signal cannot pass through walls, making it particularly useful in courtrooms, where confidential information is often discussed, and in buildings where competing signals can be a problem, such as classrooms or movie theaters. However, infrared systems cannot be used in environments with too many competing light sources, such as outdoors or in strongly lit rooms.

Personal amplifiers are useful in places in which the above systems are unavailable or when watching TV, being outdoors, or traveling in a car. About the size of a cell phone, these devices increase sound levels and reduce background noise for a listener. Some have directional microphones that can be angled toward a speaker or other source of sound. As with other ALDs, the amplified sound can be picked up by a receiver that the listener is wearing, either as a headset or as earbuds.

Induction Loop System
A loop system can assist a person with a hearing loss or hearing impairment who may use a hearing aid or cochlear implant or Loop listeners (Bellman & Symfon Audio Maxi) ® to hear sounds more clearly by reducing or eliminating background noise.

How a Loop System Works
The system begins with the sound source – a microphone placed in front of the person speaking or from a direct connection from another sound source, such as a sound system.

This sound sends a signal to a loop amplifier, that feeds an induction loop cable.  The induction loop cable circles the listening area, producing an electric current which generates a magnetic field.

The resulting electric current in the loop produces a magnetic field, which corresponds to the sound.

You can then pick up this magnetic field if you are sitting within the area of the loop and your hearing aid/cochlear implant or a loop listener (Bellman & Symfon Audio Maxi)® is switched to ‘T’.

You will need to adjust your own hearing instrument for volume. NB: You hearing instrument must be programmed to use “T‐coil” (refer to your Audiologist)

How can you use a loop system?
If you have a hearing instrument with a ‘T’ setting all you have to do is switch to ‘T’.

If you do not have a suitable hearing instrument you can still use a loop, but you will also need a loop listener.

Some loop listeners are worn with headphones or earphones. More than one person can benefit from a loop installed in a room as long as they each have a hearing instrument set to ‘T’, or a loop listener. You are not wired to any other equipment and you are therefore free to listen from anywhere within the loop and to move around.

Contact Us
If you would like us to assess your venue for a loop system, please contact us for a consultation, site visit and quote.

Activocal Wear

The Activocal Wear is a wearable assistive device designed to improve the quality of conversations. The Wear is unique as it amplifies what you want to hear while reducing background noise.

Easy to clip onto clothing and discreet to use, the Wear is the ideal choice to assist individuals who have difficulty hearing.

Features:

10 Microphones
Left and right channels
5cm (2″) in diameter
1cm (1/4′) deep
Weight: 28g

http://editmicro.co.za/product/activocal-wear/

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