An assistive listening device (ALD) is any type of device that can help you function better in your day-to-day communication. An ALD can be used with or without hearing aids to overcome the negative effects of distance, background noise, or poor room acoustics. So even though you have a hearing aid, ALDs can offer greater ease of hearing (and therefore reduced stress and fatigue) in many day-to-day communication situations. Hearing aids + ALDs = Better listening and better communication!
Each ALD has 3 main components: a microphone, a transmission technology and a device for receiving the signal and bringing the sound to the ear. The transmission technology allows us to divide the systems into the available technologies: Infrared, FM or Induction loop technologies. All of them are good but have their advantages and disadvantages.
What are Infrared Systems?
Infrared Systems utilize light based technology that is invisible to the eye to carry the signal. They guarantee privacy because light does not pass through walls. They are commonly used in court proceedings and TV listening systems. However they require a direct line of sight to the transmitting device. This means that when not in direct line of sight static can be heard and thus interfere with the transmitting signal. Great for TV viewing.
What are RF Systems?
These systems utilize RF (radio frequency) to transmit signal from transmitter to receiver. Unlike infrared units RF systems can be used also in bright light or even outdoors. The coverage range is greater than in IR systems and it does not require direct line of sight. Great for TV viewing but can also be connected to other audio sources like cd players, computers, ipods or other devices.
What are Loop Systems?
Audio Frequency Induction Loop Systems (AFL) are installed in places where hearing aid users will benefit from direct sound input to their hearing aid (Churches, community TV areas, cinemas, lectures etc.) The user switches their hearing aid to the "T"-position (Telecoil). ". A telecoil is a tiny coil of wire around a core that will induce an electric current in the coil when it's in the presence of a changing magnetic field. Some loop systems also work in combination with either IR or RF transmitter.In that case signal is transmitted via radio frequency or infra red light to the receiver connected to a necklace called neck loop, where signal is "translated" and transmitted to your hearing aids.
What are Bluetooth Systems?
The art of connecting things is becoming more and more complex every day. These days a lot of information and entertainment comes from multimedia audio devices such as TV, MP3 players, GPS and computers. All previously described systems communicate with only one device at a time while Bluetooth technology allows you to build networks of devices that transmit signal to your hearing aids. Bluetooth transmits data via low-power radio waves (RF)and it does nor rely on line of sight. It can be used in combination with loop systems using neck loop.