There are many different types of hearing assistance system. Availability varies, but generally theatres do not expect you to bring your own receiver. The only exception to this is a loop system, where a hearing aid or cochlear implant is assumed to be the receiver. For the rest of this page, I’ll use the term “hearing aid” to include cochlear implants as well, unless otherwise mentioned.
Not all hearing assistance systems require the user to have hearing aids; sometimes they just provide amplification or sound isolation for people who need more help with hearing. They almost always provide audio directly from the mixer, so there’s very little crowd noise.
Loop or telecoil
A loop system is known by many names, including: “telecoil”, “T-coil”, “hearing loop”, “induction loop”, or simply “loop”. It is the simplest system, compact, relatively cheap, and still very common. It can be found in many non-performance situations such as ticket offices and courtrooms. Loop systems are often part of the building, but portable loops do also exist, as add-ons for other systems.
Loops work by wirelessly transmitting to hearing aids by using electromagnetic induction. The hearing aid then converts this to sound, in a very similar way to a normal speaker. There’s no processing involved, so it’s effectively instantaneous.
However, a loop receiver needs to be built into the hearing aid itself, and the user needs to switch their hearing aid to the “T” position to use it. Unfortunately the telecoil receiver is starting to be phased out of newer hearing aids, and may not always be an option.
FM Radio
Radio-based systems are very similar to hearing loops, and work on a similar principle. However, they use their own receiver pack and generally provide earbuds or headphones to the user. This means they can be used by people who don’t have hearing aids, or whose hearing aids do not have a “T” setting.
Just like with a loop system, radio transmitters/receivers are effectively instantaneous, so sound arrives at almost the same time it would from the speakers… perhaps even very slightly sooner!
Infrared
Unlike the other systems described here, infrared is limited to line-of-sight. This means that there must be an unobstructed direct path between the emitter (sometimes called a “radiator”) and the receiver. Think of it as a bit like a remote control: if you cover the front of it, the device won’t receive a signal.
Infrared receivers generally need to face the stage, and their sound can be interrupted by latecomers, tall people, or other kinds of movement. Despite this, they are still useful and again provide instantaneous sound.
WiFi
There are two common WiFi-based systems for distributing sound to customers: Sennheiser MobileConnect and Williams WaveCAST. Both require an app on a smartphone to receive the sound and transmit it to the user. Theatres will provide a loaner smartphone (generally an older iPhone) with earbuds if they have this system. It is possible to install the apps on your own phone (whether iOS or Android), but you may not be able to connect to the special WiFi network used for the audio.
Unfortunately this system is… pretty terrible, in my opinion. Using a smartphone rather than a special-purpose device means that it can be distracting for people around you if you want to adjust it, and the audio stream can occasionally cut out and require you to reconnect or even restart the app to get the sound back.
Even worse: the audio has a significant delay. This means that any residual sound you can hear live (from the stage or the theatre’s speakers) is followed a few milliseconds later by an “echo” from the smartphone app. Turning the app up loud enough to drown out any residual sound is [a] bad for your hearing and [b] not always possible, and the sound you hear is then slightly offset from the actors’ mouth movements, which also ends up making it harder to understand.
To any theatres reading this: I strongly recommend avoiding these systems if you can. They might sound attractive or convenient, but please choose literally anything else, for the sake of your patrons.
Auracast (Bluetooth broadcast)
Auracast is a new technology that is just starting to emerge on the market in early 2023. The hope is that it will make its way into devices in another year or two, but it will take some time to become common.
Rather than having one-to-one connections like existing Bluetooth audio streams, Auracast allows a single transmitter to stream to multiple receivers simultaneously. If this is built into future hearing aids, it could allow a more modern equivalent of a hearing loop.
West End Access 