Infrastructure‎ > ‎Hardware‎ > ‎Audio‎ > ‎

Assistive Listening Systems


An Assistive Listening System ("ALS") helps people who are hearing-impaired to better hear the aural program content of an event, meeting, worship service, etc. An ALS is a subsystem within the realm of Live Sound Reinforcement systems.

Why use an ALS?
hearing aid uses a tiny microphone mounted inside the listener's ears to capture an "acoustic signal" (talking, etc.). The problem with this is that, if the source (e.g. pastor, loudspeakers, etc.) of the acoustic signal is located too far away from the listener's ears, then acoustic room reflections, background noise and physical obstructions can distort the original acoustic signal so much that it is unintelligible after being amplified by the hearing aid. This type of problem is very common in large rooms or event venues where the hearing-impaired person is trying to listen to event program material (not merely talking with the person sitting next to him/her).

An assistive listening system solves this problem by getting its signal from a microphone mounted at the source of the signal, or even directly from an audio output of the venue's audio system. Then, the ALS takes this audio signal and sends it in a manner of high fidelity and special signal processing either to the listener's personal hearing aid (even cochlear implants!) or to an assistive listening device that the hearing-impaired listener wears like a hearing aid. Overall, you can see how an ALS ensures that the hearing-impaired listener experiences the best signal possible.

Types of ALS
Note: All of these systems are called "wireless" because the user does not need to connect to the ALS audio mixer with a piece of wire. Instead, the user receives the signal through the air.

  1. Low-Frequency Induction Loop Wireless Systems
    • A loop of wire is mounted in the floor or on/in the walls of the venue, to serve as an electromagnetic transmission antenna.
    • Personal hearing aids that are embedded with receiving antennas called "Telecoils" ("T-coils") can receive the signal transmitted from the loop. As of the year 2013, many hearing aids come with Telecoils embedded, including cochlear implants! This means that, quite often, no extra equipment besides the induction loop system is necessary.
    • Additionally, pocket-sized Telecoil receivers (and earphones) can be handed out to hearing-impaired persons at events.
    • Functions best as a permanent installation.
    • If your organization is planning to build a new facility or to renovate and old one, and if your organization wants to use an ALS, then it is important to get plans for ALS installation added to the construction plans as soon as possible. In large venues, several loop antennas may be necessary to cover the entire venue. Also, large venues tend to have a lot of high-power electrical equipment, which may cause noise and warrant modification to the construction plans.
    • Also used in portable applications, but it can be tricky due to the possibility of trip hazards. Typically, the induction loop wire is laid on the ground, around the perimeter of the venue, or at least around the area where hearing-impaired persons are planning to sit.
    • Of all the systems available in the year 2013, the Induction Loop provides the best features to hearing-impaired persons.
  2. High-Frequency RF FM Wireless Systems
    • RF = Radio Frequency. FM = Frequency Modulation.
    • A low-power radio transmitter sends signal to pocket-sized receivers. Regular earphones are plugged into the receiver.
    • Functions anywhere, and is especially useful in portable applications.
    • Not capable to interface to the hearing-impaired person's personal hearing aid nor cochlear implant. Earphones or headphones are necessary.
    • Sometimes significantly less expensive than permanently installing an induction loop system. Depends upon your organization's circumstances.
  3. IR Wireless Systems
    • IR = Infrared, the frequencies of light just a little lower than the color red, invisible humans.
    • Super-bright IR transmitters (basically bright lights that are invisible to humans) are mounted around the perimeter of the venue. Regular earphones are plugged into pocket-sized receivers.
    • This type of system functions only indoors, and is impaired by such factors as:
      1. Line-of-sight is necessary between the transmitter and the receiver. Heads, arms, etc. can block the signal.
      2. Venue lighting that transmits light in the IR spectrum can create interference.
      3. Windows that allow daylight into the venue can create interference.
    • Not capable to interface to the hearing-impaired person's personal hearing aid nor cochlear implant. Earphones or headphones are necessary.
    • IR systems are becoming obsolete.

Notes
  1. Some events may not even need any audio equipment except an ALS. (Although many ALS do not come with a microphone, built-in mixer or connecting cables. Check your system's components and features.)
  2. Most wireless In-Ear-Monitor ("IEM") systems that are used by worship bands are not designed to be used as an ALS.
    • A genuine ALS has special signal processors that help the audio technician to adjust the signal in special ways to make everything sound better to a hearing-impaired person. These special changes often do not sound good to people with normal hearing.
    • Just as the special signal processing of an ALS will likely not sound good to a person who has normal hearing, a plain old IEM system used for bands likely will not sound good to a person who is hearing-impaired.
    • In a pinch, an audio technician could possibly use an IEM to help a hearing-impaired person, but the hearing-impaired listener would likely significantly benefit from the technician making some changes to the EQ settings (and do some more complex signal processing if he knows how).

For more information regarding Assistive Listening Systems, please consult your owner's manual or visit the LSR Training & Tutorials page of this wiki.


---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Pastor Nathan Ericson - Martin Luther, Oshkosh

Installing a hearing loop will result in better hearing for more people than with a wireless hearing system. See the article on p. 23 of the November 2010 Forward in Christ. At our church, instead of 2 or 3 people using the old wireless system and hearing rather poorly with it, we have 15 to 20 people using the hearing loop, and hearing well with it.

See the following page on our website, along with attachments at the bottom of the page:

http://www.martinlutheroshkosh.com/hearing-loop
Also visit the following websites:

http://www.hearingloop.org
http://www.foxvallinghearingloop.com

Ryan Rosenthal

Faith in Fond du Lac also put in a hearing loop with T-coil. From what I am told it is in with the mic system so that it only is amplifying what you want to hear, not every paper shuffle or child crying.

Pastor Tim Wagner

I serve on the WELS Mission for the Deaf & Hard of Hearing (MDHH). The Telecoil loops that Pastor Ericson and Mr. Rosenthal have mentioned seem the best way to go. As I understand it, it is a wire loop that you install around the base of a room that basically turns hearing aids equipped with the telecoil technology into another speaker on your PA system, so that it's like the person wearing the hearing aid is as close to the speaker as the microphone is to the speaker's mouth.

For more information about looping from MDHH, visit www.wels.net/mdhh, and click on "For Congregations." Dr. Juliette Sterkens, who was copied on this email by Pastor Ericson, is also a great resource on this issue. She is an audiologist with www.loopwisconsin.com who made a presentation at this past summer's OWLS convention. Contact information for MDHH is also on our website.

Jason Wignet

That is correct. However, don't just connect the technology to your existing PA system without working with an audio engineer to ensure you are up to snuff with the audio. You have to make sure that you are feeding "clean" audio into the coil system. Consider that the audio needs to clean and crisp, as well as free of background noises of the sanctuary, free of hum in the system, etc. 

How do you know if you need help? You can start by putting your ear up to your existing speaker and listen, would you want that in your ear canal? Do you have remote audio in your building, go that location and listen for clarity and what you hear and don't hear. Do you feel your sanctuary congregational audio through the system when singing? Maybe you will need a different feed that runs in parallel with your PA system?

Also, there are other systems out there that can be added later...but are not recommended. Those are the IR (infrared) and RF (radio frequency) systems, those were mentioned previously. Those require someone to do something to go get it and then "look different" while using them.

If you are going to be doing a flooring or remodeling project, that is the best time to think about the loop systems. Make sure that you consider help from the pre-sales engineers, because you don't want to put it in wrong when you are laying materials under carpet and tile.
Comments