Key Takeaways:
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- Infrared (IR) assistive listening systems use invisible light waves to deliver sound directly to listeners. This can help reduce the effects of distance, background noise and room reverberation, making speech and audio easier to understand.
- IR assistive listening systems are widely used in theaters, auditoriums, meeting rooms, houses of worship and other indoor spaces.
- Listeners typically use a receiver provided by the venue to access an IR transmission. Depending on their assistive devices, they may listen through headphones, earbuds or a neckloop connected to a compatible hearing aid or cochlear implant.
- IR systems work best indoors and usually require a clear path between the transmitter and receiver. For this reason, room design and receiver placement can be important factors in system performance.
What is an Infrared (IR) Assistive Listening System?
Infrared (IR) assistive listening systems use invisible infrared light to transmit sound from a microphone, public address system, television or other audio source to a receiver worn by the listener. They are one of the established technologies used in assistive listening systems in theaters, auditoriums, houses of worship, classrooms, meeting rooms and other public spaces.
How does an infrared system work?
An IR assistive listening system (ALS) converts an audio signal into a form that can be carried by infrared light. A transmitter, connected to the venue’s sound system, sends the signal to one or more infrared emitters. The emitters distribute the infrared signal through the room. A listener’s infrared receiver detects the light signal and converts it back into an audio signal.
Infrared light is similar to the technology used in a television remote control, although an ALS is designed to transmit a continuous audio signal rather than a series of remote-control commands. The IR signal is invisible to the human eye.
Infrared transmission generally requires a line of sight between the emitter and receiver. The signal can be blocked by walls, furniture, people or other objects. For this reason, the location and number of infrared emitters are important when designing a system for a large room. Listeners may also need to sit where the receiver has a good view of an emitter.
Another characteristic of IR transmission is its sensitivity to strong ambient light. Direct sunlight can interfere with reception, which makes traditional IR systems primarily an indoor technology. Within a properly designed indoor space, however, infrared can provide reliable coverage.
Where are infrared systems used?
Infrared ALS are commonly found in theaters, auditoriums, conference rooms, houses of worship, courtrooms, classrooms and other indoor assembly areas. A theater, for example, may connect its IR transmitter to the same sound system used for the performance. A person who requests assistive listening can receive an IR receiver from the venue and listen to the performance through headphones or another compatible device.
Infrared can also be used when multiple audio channels are needed. For example, a venue may use different channels to provide translations or other audio content. Because IR signals generally remain within the enclosed space where they are transmitted, this can also be a useful solution when a venue wants to limit the signal to a particular room.
Infrared technology is not restricted to public venues. Similar systems can be used at home, such as for listening to television. In these applications, an IR transmitter connected to the television sends the audio to an IR receiver, which may be built into a set of headphones.
How infrared differs from other transmission technologies
Assistive listening systems all have the same basic goal: to bring the desired sound closer to the listener while reducing the effects of distance, background noise and room reverberation. The primary difference is how the signal travels from the sound source to the listener.
Infrared systems transmit the signal using light rather than radio waves, a magnetic field or a computer network. Unlike FM systems, IR generally requires line of sight and can be affected by sunlight. Unlike a hearing loop, an IR system does not send the signal directly into a hearing aid’s telecoil. Unlike a Wi-Fi system, it does not depend on the venue’s Wi-Fi network or an internet connection. Meanwhile, the newest ALS technology, Auracast,™ is based on Bluetooth Low Energy broadcast audio.
Infrared can therefore be particularly useful in indoor spaces where the transmission area needs to be controlled. FM and some Wi-Fi systems can cover areas beyond the room in which the transmitter is located, while IR transmission is generally contained by the physical characteristics of the room.
What equipment does a listener need?
A listener normally needs an infrared receiver to access the signal. The receiver may be a small body-worn unit or another device supplied by the venue. The receiver typically connects to headphones, earbuds or another listening device.
People who use hearing aids or cochlear implants may be able to use a neckloop or similar accessory with the IR receiver. The neckloop converts the electrical audio signal from the receiver into a magnetic signal that can be picked up by a telecoil in a compatible hearing aid or cochlear implant processor. This allows the listener to use the hearing device rather than conventional headphones.
Some venues may provide headphones or earbuds with their receivers, while others may provide receivers that can be used with the listener’s own accessories. The exact equipment available varies by system and venue.
When attending a venue with an infrared assistive listening system, it can be useful to ask in advance what type of receiver is provided and whether a neckloop is available for people who use hearing aids or cochlear implants.
FAQs
An infrared assistive listening system uses invisible light to transmit sound from a microphone, public address system, television or other audio source to a listener. The technology is commonly used in public venues to improve access to speech and audio.
An IR system converts sounds into a signal carried by infrared light. Emitters distribute that signal throughout a room, and a receiver worn by the listener detects the light signal and converts it back into sound.
Traditional infrared systems are primarily designed for indoor use. Strong ambient light, including direct sunlight, can interfere with reception and affect performance. Infrared assistive listening systems can be found in theaters, auditoriums, conference rooms, houses of worship, classrooms and courtrooms. They can also be used at home for television listening and other personal applications.
Infrared systems transmit audio using light rather than radio waves, magnetic fields or computer networks. Unlike most other assistive listening technologies, IR generally requires line of sight between the transmitter and receiver.
Because IR signals are generally contained within the room where they are transmitted, venues can provide assistive listening without extending the audio signal into adjacent spaces. Infrared systems can also support multiple audio channels, such as language interpretation or other supplemental audio content.
Most IR systems require an infrared receiver supplied by the venue. The receiver may connect to headphones, earbuds or a neckloop. People who use hearing aids or cochlear implants with telecoils may be able to connect through a neckloop rather than using conventional headphones.