What are Assistive Listening Systems (ALS)?
Assistive Listening Systems (ALS) help individuals with hearing loss hear speech and sound more clearly—especially in environments with background noise, distance, or poor acoustics.
These systems transmit sound directly from the source (like a microphone) to the listener’s ear or hearing device, improving speech clarity and reducing unwanted sound.
ALS can be used:
- With hearing aids or cochlear implants
- Without hearing aids (using headphones or earbuds)
ALS are especially useful for people who can understand speech when it’s properly amplified and directed.
Why Not Just Use Hearing Aids or PA Systems?
Hearing aids are excellent in quiet settings but can struggle in noisy spaces. They may amplify sounds other than what is necessary for comminucation, including background noise, which makes distinguishing speech sounds more difficult.
Public address (PA) systems, while designed to project sound, often suffer from issues like:
- Echo and distortion
- Poor acoustic design (bare floors, hard walls, high ceilings)
- Overamplification that reduces speech clarity
ALS systems solve these challenges by transmitting sound directly from the source to the listener, improving signal-to-noise ratio (SNR)—the balance between the “signal” (what you want to hear) and the “noise” (everything else).
Modern hearing aids now include directional microphones and digital noise reduction, but ALS still provide more consistent clarity in classrooms, theaters, meeting halls, and places of worship.
How Do Assistive Listening Systems Work?
An ALS captures sound from the source and transmits it directly to a personal receiver used by the listener. This minimizes the effects of:
- Distance from the speaker
- Room acoustics
- Background noise
If a venue already has a PA system with a soundboard, the ALS can often connect directly to it. Listeners can then adjust their personal volume controls without affecting anyone else.
Types of Assistive Listening Systems
Infrared (IR)
- Uses infrared light to transmit sound.
- Common in movie theaters, courtrooms, and conference rooms.
- Signals do not pass through walls, preserving privacy and reducing interference.
FM (Radio Frequency)
- Uses radio waves to transmit sound.
- Effective in classrooms, auditoriums, and large venues.
- Requires the receiver to be tuned to the same channel as the transmitter.
- Some modern FM systems include encrypted digital transmission for improved reliability.
Audio Induction Loop (Hearing Loop)
- Sends sound via an electromagnetic field directly to hearing aids or cochlear implants equipped with a telecoil (T-coil).
- Ideal for permanent installations like churches, lecture halls, airport counters, and meeting rooms.
- Provides seamless listening with no additional receivers for T-coil users.
Digital and Bluetooth-Based Systems
- Newer systems use Bluetooth LE Audio or WiFi streaming technology.
- Allow listeners to connect via smartphones or Auracast enabled hearing devices, and legacy users through specialized receivers. Please note that Auracast is a new technology and standards have not yet been fully implemented.
- Often used in universities, airports, and museums for personal or group listening.
Hardwired Systems
- Older but still useful in smaller venues.
- Listeners plug in directly via cables connected to an audio amplifier.
- Simple, low-maintenance setup for consistent users in fixed locations.
What Components Make Up an Assistive Listening System?
Most ALS types include the following parts:
- Microphone or patch cord: Captures sound from the source.
- Transmitter: Sends the sound using infrared light, radio frequency, loop signals, or digital wireless.
- Receiver: Worn by the listener (bodypack, smartphone, or integrated device).
- Listening attachment: Delivers sound directly to the ear or hearing device.
Newer systems often integrate receivers into smartphones or hearing aids, allowing users to adjust settings via mobile apps or touch controls.
Listening Attachments
The right accessory ensures comfort and sound quality. Common types include:
- Headphones or earphones: Deliver sound directly but may not fit well with hearing aids.
- Single or double earbuds: Useful for discrete, one-ear listening.
- Neck loops or silhouettes: Use electromagnetic coupling with telecoil-equipped hearing aids.
- Patch cords: Connect receivers to cochlear implants or hearing aids with direct audio input.
Accessibility Standards and Resources
Under the Americans with Disabilities Act (ADA), many public venues are required to provide assistive listening systems to ensure effective communication access.
Key resources and guidelines:
- ADA.gov – Effective Communication
- ADA and Massachusetts Employment Discrimination Law
- Hearing Loss Association of America (HLAA)
For the latest ALS technologies and best practices, visit manufacturers such as Listen Technologies and Williams AV.