The South African Society of Hearing Aid Acousticians

ASSISTIVE LISTENING DEVICES
Assistive listening devices (ALDs) can dramatically improve communication in difficult listening situations.

Thanks to modern hearing instrument technology, people with hearing loss are now able to hear and understand clearly in many everyday situations. Nevertheless, Assistive Listening Devices can provide additional benefits to many hearing impaired individuals.

Your personal needs are determined by the characteristics of your hearing loss and your lifestyle. You hearing healthcare professional is the person best qualified to advise you which ALDs could improve the quality of your life.

WHEN CAN ASSISTIVE LISTENING DEVICES BE BENEFICIAL?

Generally speaking, you should consider using an ALD if situational barriers to communication prevent you from understanding others. The following three factors have a negative impact on the quality of the signal received by your hearing instruments:

1. Noisy backgrounds, e.g. at public events, in restaurants, while driving
2. Distance from the person speaking, e.g. conferences or guided tours
3. Places with a high level of reverberation, e.g. large halls

Many of the things we enjoy most in life take place in environments where even people with good hearing often have difficulty understanding: social and business occasions, lectures, cars, public transport, sporting events, religious ceremonies, or listening to guided tours.

HOW ALDs WORK…

A microphone is placed close to sound source you wish to hear: e.g. your conversation partner in a car; the speaker at a university lecture, the TV set, etc. The speech signal is transmitted directly to your hearing instruments.

... AND HOW YOU CONNECT THEM TO YOUR HEARING INSTRUMENTS

To connect an ALD, your hearing instrument must have an audio input facility. This is a built-in connection, which enables the signal to be transmitted directly into your hearing instrument without being picked up first by its microphone. Audio-input is commonly available only in Behind-the-Ear (BTE) instruments.

The audio shoe is attached to the hearing instrument, where it serves as a bridge between the hearing instrument and the ALD. Most ALDs are connected to the audio shoe by a cable. There are also some, which have a radio connection to the audio-shoe, and require no cable.

Different types of ALDs at a glance

1. WIRELESS COMMUNICATION SYSTEMS

Essentially, wireless communication systems consist of two components: a microphone with a transmitter and a receiver connected to a hearing instrument. The speaker’s voice is conveyed as a radio signal – i.e. without a cable connection – from the transmitter to the receiver. These systems are extremely convenient to use, have a long range and are suitable for indoor and outdoor use. Several types of wireless communication systems have been manufactured, and your hearing aid acoustician can advise you the compatibility with hearing instruments.

A) Microphone/transmitter units

Type A: The microphone and transmitter are worn by the person you wish to hear. The microphone is connected to a transmitter via a cable. This unit is particular suitable for lectures, school and guided tours.

Type B: The transmitter and microphone are housed in a single unit. This device can be held by the hearing instrument user who directs it toward the person he/she is listening to.

B) Receivers and hearing instrument connection

Type A: The receiver is worn by the hearing instrument user and is connected to the hearing instrument with a cable. This system, where the speaker wears the transmitter and the hearing instrument user the receiver, is ideal for lectures, seminars, conferences, noisy work environments, etc.

Type B: In this tiny ultra-light system, the receiver is built into the audio shoe, eliminating the cable between receiver and hearing instrument. There are unlimited uses for this system: social and business occasions, noisy working environments, classrooms and lecture halls, churches, guided tours, sporting events, radio and TV broadcasts, private and public transport, at the theatre, concerts….

2. COMMUNICATION SYSTEMS WITH CABLE CONNECTIONS

A) Hand-held microphone

The conference microphone is useful for participating in group conversations. It can be positioned on the table and directed towards the person speaking or other specific sound resources.

B) External telephone coil

Like the coil built into the hearing instrument itself, the external telephone instrument coil functions as an inductive pick-up system. It provides additional amplification for telephone calls or in public buildings equipped with loop systems (churches, theatres, lecture and concert halls, etc), if the hearing instrument’s built-in coil has insufficient boost.

A telephone coil is a small device designed to pick up inductive signals and is found in many hearing instruments. By moving the switch on the hearing instrument to “T” or, in the case of programmable hearing instruments, pressing the “T” button on the remote control, speech signals can be picked up from hearing instrument compatible telephones or from the special loop systems found in many public buildings.

C) Telephone coupler

A telephone coupler boosts the signal and consists of an acoustic microphone with its own volume control, independent of the hearing instrument. Telephone couplers can be used also with radios and televisions, tape recorders and CD players.

D) TV/stereo-volume control

The volume control is connected directly to your television or stereo set and your hearing instruments. It enables optimum transmission and adjustment of the volume independently of the TV or stereo system.

E) In conclusion

Wherever noise, distance or reverberation seriously impede communication, Assistive Listening Devices can help to clear the barriers to better hearing and achieving excellent sound quality.

ALDs can give you a decisive improvement in your hearing and listening comfort. Your hearing aid acoustician will gladly advise you on the ALD system best suited to your particular needs.