Audiology

Assistive Listening Systems

What are ALSs?

Assistive Listening Systems (ALSs) — also called assistive listening devices (ALDs) — are amplifiers that bring sound directly into the ear. They separate the sounds, particularly speech, a person wants to hear from background noise that often makes it harder to hear those distinct sounds. They improve what is known as the “speech-to-noise ratio.”

Why are ALSs Necessary?

Research indicates that people who are hard of hearing require a volume (signal-to-noise ratio) increase of about 15–25 decibels (dB) in order to achieve the same level of understanding as people with normal hearing. An ALS allows them to achieve this gain for themselves without making it too loud for everyone else.

Can ALSs Be Used by People with Hearing Loss? 

Yes. ALSs are used by people with all degrees of hearing loss, from mild to profound. This includes hearing aid users and cochlear implant users, in addition to consumers who do not use either hearing aids or cochlear implants. Hearing aids and cochlear implants have performance limitations and don’t work well in all situations. ALSs help overcome these barriers.

Where Do People Use ALSs?

ALSs help address listening challenges in three ways: minimizing background noise; reducing the effect of distance between the sound source and the deaf or hard of hearing person; and overriding poor acoustics, such as echo. People use ALSs in places of entertainment, employment, and education, as well as for home/personal use.

What are the Types of ALSs?

ALSs utilize FM, infrared, and inductive loop technologies. Each has its advantages and disadvantages.

What Are FM Systems?

FM (frequency modulation) systems are ALSs that use radio broadcast technology. They are often used in educational settings and offer mobility and flexibility when used with portable body-worn transmitters. Some newer FM systems utilize miniaturized receivers that fit onto a hearing aid. This smaller receiver is not available through a catalogue. It must be dispensed by a hearing aid professional and is more expensive than traditional FM systems. It also uses a high frequency making it incompatible with other FM systems.

What are Infrared Systems?

ALS infrared systems operate somewhat like a television remote control, employing an infrared light to transmit a signal that is received through special receivers or headphones worn by the listener. The receiver must be within the transmitter’s line of sight. Infrared systems typically are used in large spaces like conference centers and theatres.

What are Inductive Loop Systems?

Wide-area loop systems utilize an electromagnetic field to deliver sound. They offer convenience to those who use what are called “t-coil” hearing aids (those that use a slim piece of wire to supplement hearing by detecting certain sounds, like those made by magnetic signals) because those users don’t have to wear receivers. Loop systems can be used by non-hearing aid users through use of a headphone and inductive loop receiver.

What are the Basic Parts of an ALS?

Each ALS has at least three components: a microphone, a transmission technology, and a device for receiving the signal and bringing the sound to the ear. This is important to understand in order to troubleshoot problems systematically and to improve a system’s effectiveness.

Bluetooth & Hearing Aids

Hearing aids with Bluetooth connectivity make it possible to stay connected to a number of electronic devices, including phones, televisions, and tablets.

How Does Bluetooth Work with Wireless Hearing Aids?

During the initial hearing aid consultation with the audiologist, a patient will discuss whether they need a device with wireless connectivity. If they need to connect with a mobile phone, tablet, computer, music player, or other Bluetooth-enabled device, the audiologist will recommend a set of wireless hearing aids and, if appropriate, a compatible streamer.  The wireless hearing aids can either be paired directly to a device or with the streamer, which then can be paired with external devices. The streamer will pick up the Bluetooth signal from your phone, for example, and send it to your hearing aid via an FM signal or electromagnetic field, depending on the manufacturer’s design. Usually the streamer is worn around the neck or placed in a pocket for hands-free operation.