Assistive Listening Devices
They are amplifiers that bring sound directly into the ear. They separate the sounds, particularly speech, that a person wants to hear from background noise. They improve what is known as the “speech to noise ratio.”Research indicates that people who are hard of hearing require a volume (signal to noise ratio) increase of about 15 to 25 dB in order to achieve the same level of understanding as people with normal hearing. An ALD allows them to achieve this gain for themselves without making it too loud for everyone else.ALDs are used by people with all degrees of hearing loss, from mild to profound.
This includes hearing aid users and cochlear implant users, as well as consumers who do not use either hearing aids or cochlear implants. Hearing aids or cochlear implants have performance limitations and do not work well in all situations. ALDs are sometimes described as “binoculars for the ears” because they “stretch” hearing aids and cochlear implants, thus extending their reach and increasing their effectiveness.
Types of ALDs:
- FM systems are ALDs 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 via a “boot.”
- Infrared systems are ALSs that utilize light-based technology. They guarantee privacy because light does not pass through walls. They are the appropriate choice for situations such as court proceedings that require confidentiality.
- Inductive loop utilize an electromagnetic field to deliver sound. They offer convenience to groups of t-coil hearing aid users because those users do not require body worn receivers. Loop systems can be used by non-hearing aid users through use of a headphone and inductive loop receiver.