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The Audio Description Project

All About Technology for Audio Description

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Presented by Mike Feltman, an AD equipment professional in Raleigh, NC. USA.
Last updated in February 2023, to add 'Exmax' as a manufacturer of radio frequency (RF) based audio description receivers and transmitters.

Providers -- Please contact the Webmaster if you want your business to be included in '...Suppliers Links'

Audio Description 101...What a Difference Technology Makes

Scene One:  My friend who is blind goes to a local live theater production with me. During the play, he leans over to me and whispers, "Why is the audience laughing?"  I whisper back, "the husband just pantomimed a choking motion behind his wife's back!".
Scene Two:  I go to the same play with this same friend.  As we walk through the lobby, he stops at the audio description outreach table and picks up a small radio receiver and ear piece.  We go to our seats and while I'm reading the program notes, he is listening to the pre-show audio described program notes.  He leans over to me and asks, "Did you know this play we're about to see first appeared on Broadway in 1959 and was written by Howard Linday & Russel Crouse?" The play starts, and my friend doesn't ask one question during the play...not one. We are both free to enjoy the play in our own way. Audio description is being done in both scenarios.
The difference is TECHNOLOGY!

Each technology has its own set of solutions and shortcomings.  Here we provide a brief discussion about each technology and invite you to tell us more about how your organization uses technology to deliver audio description and improve the user experience.  For users of audio description, we encourage you to tell us what works for you and what doesn't.

As we become aware of new technology, we'll add the information and links.  We'll do our best to stick to the facts but we'll also share opinions and publish information from ADP's Discussion List.  More information about the discussion list is found at the bottom of our "About This Web Site...." page.

Audio Description Technologies

This topic has four subsections...


TV networks broadcast over the airwaves, cable TV or satellite TV. In North America and Europe additional transmission equipment is used to broadcast an audio description channel containing the regular audio with the audio description added.  When your TV or your 'set-top' cable box is configured to receive the audio description channel, you hear both.

The Good News:  There are many popular TV series and TV specials in North America and Europe broadcasting AD.

The Not So Good News:  Setting up your TV to receive audio description can be a daunting task. Different providers use different technologies within the same country. Technologies are evolving and those technologies used in the United States and Europe are not standardized.

We Wish We Knew:  How networks will exploit the new digital age capability to have more than one secondary audio track to allow Spanish language, for example, to have its own audio channel instead of sharing the AD channel.

For more details about technologies used for TVs in the United States see Accessing Audio Description on Your TV.

Added April 2019 (with credit to John Paton at in the UK)
In the UK users talk about “turning on AD” and many are unaware of how AD actually arrives at their TV. In fact the UK uses two methods of broadcasting Audio Description, receiver mix and broadcast mix. In receiver mix the AD is sent on its own as a separate audio channel which is then mixed with the main audio. This has the advantage that the user can set the respective volumes although it’s not clear whether everyone is aware of this or how well it’s used. This technology is used for digital terrestrial service 'Freeview'. In broadcast mix the AD is sent pre-mixed with the main audio as a secondary audio track and the receiver just selects which audio channel to play. This is used for all other broadcast methods in the UK (cable and satellite services). For video on demand services it is common to just create a new video asset with the broadcast mix built in. Certain broadcasters started doing this because some devices didn't cope well with multiple audio tracks. It greatly reduces the complexity while just requiring more hard drive space and a tweak to the user interface.
In the rest of Europe I think everyone uses broadcast mix but this is complicated a bit by countries which have more than one official language such as Belgium and Switzerland. I think in these cases the AD is treated as a separate language track. They also have the complication of spoken subtitles to think about.
The Future of AD on TV in the UK and the Rest of Europe There’s buzz about Next Generation Audio using Object Based Audio, (NGA using OBA). This would allow the AD to be a set of tagged audio objects which can be switched on and off. It reduces the bitrate required as well as adding all the benefits of NGA such as 3D sound and alternative commentaries on sport. In Europe it’s being talked about as a logical next step although it requires a lot to happen so we don't know if or when it will happen.

Movies in Theaters

Most new movies have audio description available which can be detected and transmitted at specially equipped movie theaters.  Patrons are loaned a small receiver and a headset to pick-up the audio description, while they can hear the regular sound track 'around' the headset. Recently we used a model with the receiver built into a small headset. On each ear piece is a volume knob. Turn up the left volume knob to listen to an amplified version of the sound track. Turn up the right volume knob and listen to the audio description track.

Find out about movie theaters offering AD...
Find out about companies offering systems for AD in movie theaters.

The Good News:  Most new movies are being released with audio description available. All movie theaters are now required to provide AD headsets once they install digital projectors, which most movie theaters have today

The Not So Good News:  The equipment on the movie theater side is expensive so not all movie houses have it. Theater staff may not be well trained on the setting up and use of the AD receivers, and equipment failures frequently occur despite a new law addressing these deficiencies.

We Wish We Knew:  How to drive down the cost and drive up the availability.

DVD Players

Although video tapes (VHS) have become a thing of the past, more and more digital video disks (DVDs) have a user selectable audio description sound track. No special equipment is required...just a TV or monitor and a DVD player.
Click here to find out which DVDs in the United States have audio description tracks.
The Good News:  No special equipment other than a TV and DVD player are needed. Over 1000 DVDs are available with audio description.

The Not So Good News:  Although more and more DVDs have audio description tracks, not all of them have it and purchasing DVDs for individual home use can be expensive.  Rentals may not be convenient or may be impossible in some localities.

Live Performances and Other Events without Prerecorded Audio Description
...a live audio describer is present

This is only an introduction. If you are using this information to plan a new system we encourage you to determine how and where your audio description will be delivered, the needs and preferences of your users, and your budget before contacting the vendors.

No matter what the venue and no matter whether the audio description source is live-on-site or pre-recorded, some type of transmitter-receiver technology is used. In this section we explore 1) what types of technology are available for performances and events where a live audio describer is present, and 2) which technology-ies best fit which conditions.

The 'transmitter-receiver' concept when live audio describers are present....
The audio describer’s voice is input to the transmitter, the transmitter broadcasts the audio description to receivers tuned to receive the transmitter's broadcast and the audio description is heard by the user wearing an earpiece connected to the receiver.

Transmitters can be permanently installed in venues or they can be small portable devices not much larger than a deck of cards. Receivers are typically designed to be hand-held by the user and typically have an on/off/volume control and an audio output jack for ear-speakers, ear-buds, or ear phones so as not to disturb others nearby. We see many systems where the transmitters and receivers are designed, manufactured and serviced by the same provider, but we also see systems where the transmitter is from one provider and the receivers are compatible devices from another provider. We know of some systems that rely on the user's personal cell phones for receivers. In summary, regardless of other factors there is always a transmitter and always a receiver.

Broadcast technologies (from the transmitter to the receiver)
Transmitter and receiver systems are further defined by what broadcast technologies they use; radio frequency or infrared.  In radio frequency designs, the describer's voice travels on radio waves. Radio frequency use is strictly controlled by government agencies, for example, the Federal Communications Commission (FCC) in the United States and Ofcom in Great Britain. Radio frequency is further divided into 'bands'. Examples include "Frequency Modulated" (FM), Wi-Fi, and cell phone networks like '3G' and '4G'. In infrared designs, the describer's voice travels on light waves undetectable to the human eye. Within both the radio frequency design and the infrared design, transmitters and receivers must be tuned (matched) to the same channel to ensure they can communicate without disrupting and without being disrupted by communications of other systems. For this reason, designers of systems must first learn about every venue in which they intend to provide service so they don't accidentally design/purchase a system that interferes with an existing system at the venue. Take for example an audio description provider in the south central United States who purchased a radio frequency system from a well known manufacturer. The AD provider spoke to only one venue during the initial system design phase and based on that knowledge chose a radio frequency system with single channel receivers tuned to 'Channel I' (74.7 MHz within the 72 MHz band). All was well until the AD provider tried to use the same system in a different venue across town. Unfortunately, the AD provider assumed the other venue wouldn't be affected by the Channel I broadcast, however, the other venue was also using Channel I for an existing remote emergency/alarm system to the local fire station. Lucky for the AD provider the equipment manufacturer was willing to retune the single channel receivers to another Channel within the 72 MHz band free of charge.
In general, radio frequency systems can penetrate walls to some extent.  Infrared systems can have a better sound quality, but are best when in a line-of-sight application.  Infrared systems can't go through walls, but if the installation is more permanent, infrared repeaters can be installed to circumvent the problem. Users can then walk around without the annoying 'drop out' sometimes experienced when the antennas on radio frequency systems go in and out of alignment with the receivers.

Wi-Fi and cell phone broadcasts each have their own place in the mix and although this type of technology is seldom used in 'live audio description' early in 2020 we learned of a system for iPhones and Macs that uses Wi-Fi to deliver live audio description.

In summary, the AD provider must do a great deal of up-front data gathering to ensure the equipment uses the right technology set to the right frequency.  

Live Performances and Other Events with Prerecorded Audio Description live audio describer is present

This is only an introduction. If you are using this information to plan a new system we encourage you to determine how and where your audio description will be delivered, the needs and preferences of your users, and your budget before contacting the vendors.

In this section we explore 1) what types of technology are available for performances and events where the audio description is prerecorded (no live audio describer present), and 2) which technology-ies best fit which conditions.

Prerecorded audio description dates back decades to handheld receivers distributed to attendees at museum tours, art exhibits, theme parks etc. The attendees used earphones to avoid disturbing those around them. In the earliest applications, the receiver was nothing more than a prerecorded playback device which could be started and stopped by the attendee as they progressed. The shortcoming was attendees had to proceed through the tours or exhibit along a predefined path. No provision was made to take things out of order and these technologies were not very enabling for attendees who were blind or with low vision. Next, the technology improved such that at each stop on the tour, exhibit, or park, the attendee would see (or be told) a particular channel number, tune their receiver to the channel for that particular stop and listen to the associated audio description. The next improvement in technology added a small transmitter at each stop to broadcast its message to the receiver without requiring the attendee to tune in their receiver to a particular channel. The transmitters and receivers had to be 'keyed' so only the receivers within close proximity to the described item would pick up the audio description for the item. These types of systems are ideal for attendees who were blind or with low vision, no manual entry of a channel number is required....only that they be close to the item.

Prerecorded audio description technology doesn't stop there. Modern variations use the attendee's cell phone as the receiver and use of these systems are not limited to museum tours, art exhibits, theme parks etc. Take for example prerecorded audio description for live theatre. Companies have begun to produce prerecorded audio description for use in larger (i.e. big budget) live theater productions of long running plays or musicals. "Cats" is a good example, and there are many others. These shows don't change much and can stay for many months in one venue. The attendee loads an app on their cell phone and attaches earphones so they do not disturb other patrons around them. The theater installs proprietary microphones that 'listen' for specific dialog lines. When the line is heard, the system triggers the audio description associated with that place in the dialog. A human monitor is assigned to keep track of the audio description and correct any errors in case a dialog line is missed. Systems like these are not inexpensive, thus they may not be suitable for smaller local theater where only one or two performances of any given show are scheduled. However, when the right show is at the right theater for the right amount of time, the theater can offer audio description at any performance with no prior restriction or special arrangement, just like many movie theaters do today. Imagine a future where anyone can load an app onto their cell phone and hear an audio description track for any movie, live theater, museum event, art exhibit, or theme park attraction!

We can expect to see hybrid prerecorded audio description systems similar to the above, but using FM or infrared transmitters and receivers instead of the attendee's cell phone. But then, if everybody has a cell phone...maybe not. The variations are just about endless!

Which system is best
It all depends on the specific environment, portability vs. permanent installation, the nature of the event being described, and how much the users will be moving around. In general, systems that work best for live theater won't work best for exhibits and tours and vice-versa.

The Good News:  The systems are robust, affordable by many organizations and well supported.

The Not So Good News:  There is no one perfect system. It takes a lot of research and vendor interaction to determine the best system for a given environment, and then, it is only 'best' in that environment.  What if your needs change or you want to use the same equipment in a variety of environments?  Compromise is often the only solution.

We invite providers of audio description equipment and technology to allow us to let our readers know more about your products.

Disclaimer:  Neither the ADP nor the ACB endorse any of these products or vendors.  The list below is meant to help our readers contact providers of technology.  AD environments vary.  What works well for one group in one location may be marginal or totally inadequate for another group or in another location.  We recommend you work with several vendors to find the best value for your specific application before making any purchase.  Updates to this list are welcome -- contact the webmaster.

This topic has five subsections...

Mask (stenographer) Microphones

Mask (stenographer) microphones fit over a person's mouth so others nearby can not hear what is being said. These types of microphones are useful for audio describers in live theatre environments when non-user patrons are seated nearby. When properly used they do a great job of keeping the non-user patrons from hearing the describer..

Image of describer speaking into mask mic. Talk Technologies Steno Mask

Portable Soundproof Booths

Prerecorded Audio Description in Selected Live Theater, Guides to Parks, Tours, Events and Broadcast Video

Solutions and Systems for Audio Description in Movie Theaters

Transmitters & Receivers for Live Broadcast, Theaters, Museums, Tours, Parks, etc.

This topic has four subsections.  In each listing M=Manufacturer and S=Supplier.

All System Types

American Loop Systems (S)
29 Silver Hill Road
Suite 100
Milford, MA 01757
(800) GET-LOOP
(800) 955-7204 TTY

Audio Enhancement (S)
14241 South Redwood Road
P.O. Box 2000
Bluffdale, UT 84065
(800) 383-9362

Cardinal Sound & Communication (S)
2317 Kansas Avenue
Silver Spring,MD 20910
(800) 964-3496

Centrum Sound (S)
572 LaConner Drive
Sunnyvale, CA 94078
(408) 736-6500

Durateq Division of Softeq Development Corp. (S)
(Rugged handheld devices)
1155 Dairy Ashford, Suite 125
Houston, TX 77079

HARC Mercantile, Ltd. (S)
1111 West Centre Avenue
Portage, MI 49024
(800) 445-9968 Voice/TTY

Hear More (S)
42 Executive Blvd.
Farmingdale, NY 11735
(800) 881-4327 (voice)
(800) 281-3555 (TTY)

8160 Madison Avenue
Burr Ridge, IL 60521
(800) 288-8303 voice
(800) 536-8890 TTY

iProbe Multilingual Solutions, Inc. (S)
FM Systems (72 MHz, 216 MHz), Infrared Devices, Sound Isolation Booths. (Rental and Sales). Also audio description, captions and SDH subtitles in English and foreign languages.
273 East 3rd Street, Suite 2W
New York, NY 10156
(212) 489-6035

Listen Technologies Corporation (M)
14912 Heritagecrest Way
Bluffdale, Utah 84065-4818
(800) 330-0891

NADY Systems Inc. (M)
6701 Shellmond Street
Emeryville, CA 94608
(510) 652-2411

Potomac Technology (S)
1 Church Street, Suite101
Rockville,MD 20850-4158
(800) 433-2838 voice/TTY 

Oticon, Inc. (M) (Formerly Phonic Ear, now under "FrontRow" brand)
29 Schoolhouse Road
Somerset, NJ 08873
(800) 526-3921

Sennheiser Electronic Corp. (M)
1 Enterprise Drive
Old Lyme, CT 06371
(877) 736-6434

Tour-Mate Systems (M)
1290 Blossom Drive Suite D
Victor, NY 14564

Williams Sound (M)
10321 West 70th Street
Eden Prairie,MN 55344-3459
(800) 328-6190 

FM Systems Only

Comtek (M)
357 West 2700 South
Salt Lake City, UT 84115
(800) 496-3463

You can contact this manufacturer directly via email at; however, Exmax products are typically sold through Amazon via listings like this one.

Induction Loop Systems Only
AssistiveAudio (S)
2627 Algonquin Parkway
Toledo, OH 43606
(800) 224-9295 Voice
(419) 292-2169 Fax

Oval Window Audio (M)
33 Wildflower Court
Nederland, CO 80466
(303) 447-3607 Voice/TTY

Telex (M)
9600 Aldrich Avenue, South
(800) 392-3497
(612) 884-0043 Fax

Infrared Systems Only

ALDs, Inc. (M)
#2-11220 Voyageur Way
Richmond, B.C., Canada V6X 3E1
(604) 244-0269
(800) 665-2537
(604) 270-6308 Fax

Audex (M)
710 Standard Street
Longview, TX 75604
(903) 295-8244
(800) 237-0716
(800) 283-3974 Fax

Lightspeed Technologies (M)
15812 SW Upper Boones Ferry Road
Lake Oswego,OR 97035
(503) 684-5538
(503) 684-3197 Fax

Connect with QSC
Solutions for Hearing and Visually Impaired

Siemens Hearing Instruments (M)
P.O. Box 1397
10 Constitution Avenue
Piscataway, NJ 08855
(732) 562-6600
(732) 562-6696 Fax


Wi-Fi Systems for iPhone, iPad, and Mac Only

Arts Access International's "Accesslyve" System
Contact through web site only